feat: chart support — make_chart tool with recharts rendering

Adds inline data visualisation to the chat agent. After a successful
run_query, the agent can call make_chart(chart_type, x, y, [group,
title, orientation]) and the result is rendered as a bar / line / area
/ pie chart inline in the chat thread, sourced from the previous query
result.

Backend (commands/chat.rs, models/chat.rs)
- New ChartConfig{chart_type, x, y, group?, title?, orientation?} model.
- New AgentAction::MakeChart{config} variant. Parser accepts both
  `chart_type` and the alternative `type` field name (qwen3 sometimes
  emits the latter). Validates chart_type is one of bar/line/area/pie.
- last_successful_query_result helper finds the most recent successful
  run_query in the working thread.
- MakeChart dispatcher: validates that x/y/group columns exist in the
  attached query result, emits a tool_result with the same QueryResult
  in `result` and the chart_config JSON in `text`. Mismatches surface
  as a clear error ("y column `name` is not in the last result.
  Available: company_name, legal_name, …").
- build_history compression unchanged: make_chart's tool_result text
  field (the small chart_config JSON) is included in LLM history; the
  large QueryResult.rows are NOT, since the per-tool branch only emits
  text for non-run_query tools.
- System prompt: documents make_chart with concrete usage hints
  (top-N → bar, time series → line/area, proportions → pie; skip for
  ≤2 or >500 rows). 7 new parser/dispatcher tests.

Frontend (src/components/chat/)
- recharts ^3.8 added.
- New ChartPreview component renders bar (vertical+horizontal), line,
  area, pie. Supports grouped series via the `group` config field by
  pivoting rows into a wide format. Y values coerced to numbers
  (parses strings, nulls → 0). Caps to 500 points to keep things
  responsive on huge results.
- ChatMessageView routes tool=="make_chart" tool_result through a new
  ChartToolResult that parses the config JSON from the message text
  and feeds the embedded QueryResult into ChartPreview.
- New labels/icons (BarChart3) and preview-extraction for make_chart
  in tool-call collapsed headers (`bar: carrier_name → trip_count`).

Verification: cargo test --lib 77 pass (+7), tsc clean, vitest 20
pass.

src-tauri/src/commands/chat.rs

@@ -7,7 +7,7 @@ use crate::commands::memory::{append_memory_core, read_memory_core};
 use crate::commands::queries::execute_query_core;
 use crate::error::{TuskError, TuskResult};
 use crate::models::ai::OllamaChatMessage;
-use crate::models::chat::{ChatMessage, ChatTurnResult, ContextUsage};
+use crate::models::chat::{ChartConfig, ChatMessage, ChatTurnResult, ContextUsage};
 use crate::models::query_result::QueryResult;
 use crate::state::AppState;
 use chrono::Utc;
@@ -50,6 +50,7 @@ enum AgentAction {
     Remember { note: String },
     SaveQuery { name: String, sql: String },
     FindQueries { text: String },
+    MakeChart { config: ChartConfig },
 }
 
 /// Parse the model's JSON response. Accepts both shapes the model tends to emit:
@@ -151,6 +152,55 @@ fn parse_agent_action(raw: &str) -> Result<AgentAction, String> {
             }
             Ok(AgentAction::FindQueries { text })
         }
+        "make_chart" => {
+            let chart_type = lookup("chart_type")
+                .or_else(|| lookup("type"))
+                .and_then(|v| v.as_str())
+                .ok_or_else(|| "make_chart missing `chart_type`".to_string())?
+                .trim()
+                .to_lowercase();
+            if !["bar", "line", "area", "pie"].contains(&chart_type.as_str()) {
+                return Err(format!(
+                    "make_chart `chart_type` must be one of: bar, line, area, pie. Got: {}",
+                    chart_type
+                ));
+            }
+            let x = lookup("x")
+                .and_then(|v| v.as_str())
+                .ok_or_else(|| "make_chart missing `x` column".to_string())?
+                .trim()
+                .to_string();
+            let y = lookup("y")
+                .and_then(|v| v.as_str())
+                .ok_or_else(|| "make_chart missing `y` column".to_string())?
+                .trim()
+                .to_string();
+            if x.is_empty() || y.is_empty() {
+                return Err("make_chart `x` and `y` must not be empty".into());
+            }
+            let group = lookup("group")
+                .and_then(|v| v.as_str())
+                .map(|s| s.trim().to_string())
+                .filter(|s| !s.is_empty());
+            let title = lookup("title")
+                .and_then(|v| v.as_str())
+                .map(|s| s.trim().to_string())
+                .filter(|s| !s.is_empty());
+            let orientation = lookup("orientation")
+                .and_then(|v| v.as_str())
+                .map(|s| s.trim().to_lowercase())
+                .filter(|s| !s.is_empty());
+            Ok(AgentAction::MakeChart {
+                config: ChartConfig {
+                    chart_type,
+                    x,
+                    y,
+                    group,
+                    title,
+                    orientation,
+                },
+            })
+        }
         // Legacy from earlier iterations — silently ignored at parse time so the
         // model can recover with a different action.
         "get_schema" => Err(
@@ -230,6 +280,9 @@ You operate as an agent in a single-tool-per-turn loop with hop limit {hops}. On
   {{"action":"save_query","name":"<short label>","sql":"<the SQL>"}}
     Persist a non-trivial working SELECT for reuse later. Use AFTER a successful run_query when the query is likely to be re-run. Keep `name` short and descriptive (e.g. "GMV by carrier — last 30d"). The user sees these in sidebar → Saved.
 
+  {{"action":"make_chart","chart_type":"bar","x":"<col>","y":"<col>","title":"<short title>"}}
+    Visualise the LAST successful run_query result as a chart inline. `chart_type` is one of: bar, line, area, pie. `x` and `y` MUST be column names from the previous result. Optional: `group` (column for series), `orientation` ("vertical"/"horizontal", bar only). Use after run_query when the data is aggregated and would be clearer as a chart (top-N comparisons → bar; time series → line/area; proportions → pie). Skip for tiny results (≤2 rows) and giant ones (>500 rows).
+
   {{"action":"final","text":"..."}}
     End the turn with a plain-language answer for the user. Do NOT repeat the result table — the UI shows it. Mention caveats (LIMIT, NULL filters, sampling).
 
@@ -671,6 +724,92 @@ pub async fn chat_send(
                 );
                 push_tool_result(&mut new_messages, &mut working, result);
             }
+            AgentAction::MakeChart { config } => {
+                let config_json = serde_json::to_string(&config).unwrap_or_else(|_| "{}".into());
+                push_tool_call(
+                    &mut new_messages,
+                    &mut working,
+                    "make_chart",
+                    config_json.clone(),
+                );
+
+                let result_msg = match last_successful_query_result(&working) {
+                    None => ChatMessage::ToolResult {
+                        id: new_id("res"),
+                        tool: "make_chart".to_string(),
+                        is_error: true,
+                        text: Some(
+                            "make_chart needs a successful run_query result above it. Run a SELECT first, then call make_chart."
+                                .to_string(),
+                        ),
+                        result: None,
+                        created_at: now_ms(),
+                    },
+                    Some(qr) => {
+                        if !qr.columns.iter().any(|c| c == &config.x) {
+                            ChatMessage::ToolResult {
+                                id: new_id("res"),
+                                tool: "make_chart".to_string(),
+                                is_error: true,
+                                text: Some(format!(
+                                    "x column `{}` is not in the last result. Available: {}.",
+                                    config.x,
+                                    qr.columns.join(", ")
+                                )),
+                                result: None,
+                                created_at: now_ms(),
+                            }
+                        } else if !qr.columns.iter().any(|c| c == &config.y) {
+                            ChatMessage::ToolResult {
+                                id: new_id("res"),
+                                tool: "make_chart".to_string(),
+                                is_error: true,
+                                text: Some(format!(
+                                    "y column `{}` is not in the last result. Available: {}.",
+                                    config.y,
+                                    qr.columns.join(", ")
+                                )),
+                                result: None,
+                                created_at: now_ms(),
+                            }
+                        } else if let Some(group) = &config.group {
+                            if !qr.columns.iter().any(|c| c == group) {
+                                ChatMessage::ToolResult {
+                                    id: new_id("res"),
+                                    tool: "make_chart".to_string(),
+                                    is_error: true,
+                                    text: Some(format!(
+                                        "group column `{}` is not in the last result. Available: {}.",
+                                        group,
+                                        qr.columns.join(", ")
+                                    )),
+                                    result: None,
+                                    created_at: now_ms(),
+                                }
+                            } else {
+                                ChatMessage::ToolResult {
+                                    id: new_id("res"),
+                                    tool: "make_chart".to_string(),
+                                    is_error: false,
+                                    text: Some(config_json.clone()),
+                                    result: Some(qr),
+                                    created_at: now_ms(),
+                                }
+                            }
+                        } else {
+                            ChatMessage::ToolResult {
+                                id: new_id("res"),
+                                tool: "make_chart".to_string(),
+                                is_error: false,
+                                text: Some(config_json.clone()),
+                                result: Some(qr),
+                                created_at: now_ms(),
+                            }
+                        }
+                    }
+                };
+                push_tool_result(&mut new_messages, &mut working, result_msg);
+            }
         }
 
         // Any non-RunQuery, non-Final action means the model is investigating
@@ -825,6 +964,26 @@ fn format_db_error(e: &TuskError) -> String {
     e.to_string()
 }
 
+/// Locate the most recent SUCCESSFUL run_query in the working thread and
+/// return its full QueryResult. Used by make_chart to attach data to a chart
+/// directive without relying on the model to re-send it.
+fn last_successful_query_result(messages: &[ChatMessage]) -> Option<QueryResult> {
+    for m in messages.iter().rev() {
+        if let ChatMessage::ToolResult {
+            tool,
+            is_error: false,
+            result: Some(qr),
+            ..
+        } = m
+        {
+            if tool == "run_query" {
+                return Some(qr.clone());
+            }
+        }
+    }
+    None
+}
+
 /// Pull the most recent run_query error text from the working thread, so the
 /// post-loop "I gave up" summary can quote concrete errors back to the user.
 fn last_run_query_error(messages: &[ChatMessage]) -> Option<String> {
@@ -1307,6 +1466,119 @@ mod tests {
         assert!(last_run_query_error(&msgs).is_none());
     }
 
+    #[test]
+    fn parses_make_chart_minimal() {
+        let a = parse_agent_action(
+            r#"{"action":"make_chart","chart_type":"bar","x":"carrier","y":"trips"}"#,
+        )
+        .unwrap();
+        match a {
+            AgentAction::MakeChart { config } => {
+                assert_eq!(config.chart_type, "bar");
+                assert_eq!(config.x, "carrier");
+                assert_eq!(config.y, "trips");
+                assert!(config.group.is_none());
+                assert!(config.title.is_none());
+            }
+            _ => panic!("wrong variant"),
+        }
+    }
+
+    #[test]
+    fn parses_make_chart_with_group_and_title() {
+        let a = parse_agent_action(
+            r#"{"action":"make_chart","chart_type":"line","x":"month","y":"revenue","group":"region","title":"Revenue"}"#,
+        )
+        .unwrap();
+        match a {
+            AgentAction::MakeChart { config } => {
+                assert_eq!(config.group.as_deref(), Some("region"));
+                assert_eq!(config.title.as_deref(), Some("Revenue"));
+            }
+            _ => panic!("wrong variant"),
+        }
+    }
+
+    #[test]
+    fn make_chart_accepts_alternative_field_name_type() {
+        // Some models emit `type` instead of `chart_type`.
+        let a = parse_agent_action(
+            r#"{"action":"make_chart","type":"pie","x":"label","y":"value"}"#,
+        )
+        .unwrap();
+        match a {
+            AgentAction::MakeChart { config } => assert_eq!(config.chart_type, "pie"),
+            _ => panic!("wrong variant"),
+        }
+    }
+
+    #[test]
+    fn rejects_make_chart_with_unknown_chart_type() {
+        let r = parse_agent_action(
+            r#"{"action":"make_chart","chart_type":"radar","x":"a","y":"b"}"#,
+        );
+        assert!(r.is_err());
+    }
+
+    #[test]
+    fn rejects_make_chart_missing_x_or_y() {
+        assert!(parse_agent_action(r#"{"action":"make_chart","chart_type":"bar","y":"a"}"#).is_err());
+        assert!(parse_agent_action(r#"{"action":"make_chart","chart_type":"bar","x":"a"}"#).is_err());
+    }
+
+    #[test]
+    fn last_successful_query_result_finds_recent() {
+        use crate::models::query_result::QueryResult;
+        let qr = QueryResult {
+            columns: vec!["a".into()],
+            types: vec!["INT4".into()],
+            rows: vec![vec![Value::Number(1.into())]],
+            row_count: 1,
+            execution_time_ms: 1,
+        };
+        let msgs = vec![
+            ChatMessage::ToolResult {
+                id: "r1".into(),
+                tool: "run_query".into(),
+                is_error: false,
+                text: None,
+                result: Some(qr.clone()),
+                created_at: 1,
+            },
+            ChatMessage::ToolResult {
+                id: "r2".into(),
+                tool: "run_query".into(),
+                is_error: true,
+                text: Some("oops".into()),
+                result: None,
+                created_at: 2,
+            },
+        ];
+        let found = last_successful_query_result(&msgs).expect("ok");
+        assert_eq!(found.columns, vec!["a".to_string()]);
+    }
+
+    #[test]
+    fn last_successful_query_result_skips_non_run_query() {
+        use crate::models::query_result::QueryResult;
+        let qr = QueryResult {
+            columns: vec!["a".into()],
+            types: vec!["INT4".into()],
+            rows: vec![],
+            row_count: 0,
+            execution_time_ms: 0,
+        };
+        let msgs = vec![ChatMessage::ToolResult {
+            id: "r1".into(),
+            tool: "list_tables".into(),
+            is_error: false,
+            text: Some("public.x".into()),
+            result: Some(qr),
+            created_at: 1,
+        }];
+        assert!(last_successful_query_result(&msgs).is_none());
+    }
+
     #[test]
     fn render_thread_for_summary_includes_roles_and_skips_rows() {
         let msgs = vec![