refactor(ai): consolidate AI around chat tool-calling; add OpenRouter

- rework chat backend (chat.rs, chat_tools.rs, ai.rs, models, state) around tool calls
- add OpenRouter provider alongside Ollama/Fireworks in settings
- drop inline AiBar, ResultsPanel explain/fix UI and ChartPreview in favour of the chat panel
- add frontend chat tool-registry

src-tauri/src/models/ai.rs

@@ -1,13 +1,26 @@
-use serde::{Deserialize, Serialize};
+use serde::{Deserialize, Deserializer, Serialize};
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize, Default)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Default)]
 #[serde(rename_all = "lowercase")]
 pub enum AiProvider {
     #[default]
     Ollama,
-    OpenAi,
-    Anthropic,
     Fireworks,
+    OpenRouter,
+}
+
+/// Deserialize a provider string, coercing legacy `openai`/`anthropic` and any
+/// unknown value to `Ollama`. Keeps existing config files loadable after the
+/// stub providers were removed.
+impl<'de> Deserialize<'de> for AiProvider {
+    fn deserialize<D: Deserializer<'de>>(d: D) -> Result<Self, D::Error> {
+        let s = String::deserialize(d)?;
+        Ok(match s.as_str() {
+            "fireworks" => AiProvider::Fireworks,
+            "openrouter" => AiProvider::OpenRouter,
+            _ => AiProvider::Ollama,
+        })
+    }
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
@@ -15,11 +28,9 @@ pub struct AiSettings {
     pub provider: AiProvider,
     pub ollama_url: String,
     #[serde(default)]
-    pub openai_api_key: Option<String>,
-    #[serde(default)]
-    pub anthropic_api_key: Option<String>,
-    #[serde(default)]
     pub fireworks_api_key: Option<String>,
+    #[serde(default)]
+    pub openrouter_api_key: Option<String>,
     pub model: String,
 }
 
@@ -28,9 +39,8 @@ impl Default for AiSettings {
         Self {
             provider: AiProvider::Ollama,
             ollama_url: "http://localhost:11434".to_string(),
-            openai_api_key: None,
-            anthropic_api_key: None,
             fireworks_api_key: None,
+            openrouter_api_key: None,
             model: String::new(),
         }
     }
@@ -71,7 +81,9 @@ pub struct OllamaModel {
 }
 
 // ---------------------------------------------------------------------------
-// Fireworks (OpenAI-compatible chat-completions)
+// OpenAI-compatible chat-completions (Fireworks, OpenRouter)
+// These request/response shapes are shared by every OpenAI-compatible provider;
+// the `Fireworks*` names are retained for historical reasons.
 // ---------------------------------------------------------------------------
 
 #[derive(Debug, Clone, Serialize)]