feat: add embedded MCP server and Makefile

Add an MCP (Model Context Protocol) server that starts on 127.0.0.1:9427
at app launch, sharing connection pools with the Tauri IPC layer. This
lets Claude (or any MCP client) query PostgreSQL through Tusk's existing
connections.

MCP tools: list_connections, execute_query, list_schemas, list_tables,
describe_table.

Also add a Makefile with targets for dev, build (cross-platform),
install/uninstall, lint, and formatting.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src-tauri/src/commands/schema.rs

@@ -3,11 +3,12 @@ use crate::models::schema::{ColumnDetail, ColumnInfo, ConstraintInfo, IndexInfo,
 use crate::state::AppState;
 use sqlx::Row;
 use std::collections::HashMap;
+use std::sync::Arc;
 use tauri::State;
 
 #[tauri::command]
 pub async fn list_databases(
-    state: State<'_, AppState>,
+    state: State<'_, Arc<AppState>>,
     connection_id: String,
 ) -> TuskResult<Vec<String>> {
     let pools = state.pools.read().await;
@@ -27,15 +28,14 @@ pub async fn list_databases(
     Ok(rows.iter().map(|r| r.get::<String, _>(0)).collect())
 }
 
-#[tauri::command]
-pub async fn list_schemas(
-    state: State<'_, AppState>,
-    connection_id: String,
+pub async fn list_schemas_core(
+    state: &AppState,
+    connection_id: &str,
 ) -> TuskResult<Vec<String>> {
     let pools = state.pools.read().await;
     let pool = pools
-        .get(&connection_id)
-        .ok_or(TuskError::NotConnected(connection_id))?;
+        .get(connection_id)
+        .ok_or_else(|| TuskError::NotConnected(connection_id.to_string()))?;
 
     let rows = sqlx::query(
         "SELECT schema_name FROM information_schema.schemata \
@@ -50,15 +50,22 @@ pub async fn list_schemas(
 }
 
 #[tauri::command]
-pub async fn list_tables(
-    state: State<'_, AppState>,
+pub async fn list_schemas(
+    state: State<'_, Arc<AppState>>,
     connection_id: String,
-    schema: String,
+) -> TuskResult<Vec<String>> {
+    list_schemas_core(&state, &connection_id).await
+}
+
+pub async fn list_tables_core(
+    state: &AppState,
+    connection_id: &str,
+    schema: &str,
 ) -> TuskResult<Vec<SchemaObject>> {
     let pools = state.pools.read().await;
     let pool = pools
-        .get(&connection_id)
-        .ok_or(TuskError::NotConnected(connection_id))?;
+        .get(connection_id)
+        .ok_or_else(|| TuskError::NotConnected(connection_id.to_string()))?;
 
     let rows = sqlx::query(
         "SELECT t.table_name, \
@@ -70,7 +77,7 @@ pub async fn list_tables(
          WHERE t.table_schema = $1 AND t.table_type = 'BASE TABLE' \
          ORDER BY t.table_name",
     )
-    .bind(&schema)
+    .bind(schema)
     .fetch_all(pool)
     .await
     .map_err(TuskError::Database)?;
@@ -80,16 +87,25 @@ pub async fn list_tables(
         .map(|r| SchemaObject {
             name: r.get(0),
             object_type: "table".to_string(),
-            schema: schema.clone(),
+            schema: schema.to_string(),
             row_count: r.get::<Option<i64>, _>(1),
             size_bytes: r.get::<Option<i64>, _>(2),
         })
         .collect())
 }
 
+#[tauri::command]
+pub async fn list_tables(
+    state: State<'_, Arc<AppState>>,
+    connection_id: String,
+    schema: String,
+) -> TuskResult<Vec<SchemaObject>> {
+    list_tables_core(&state, &connection_id, &schema).await
+}
+
 #[tauri::command]
 pub async fn list_views(
-    state: State<'_, AppState>,
+    state: State<'_, Arc<AppState>>,
     connection_id: String,
     schema: String,
 ) -> TuskResult<Vec<SchemaObject>> {
@@ -122,7 +138,7 @@ pub async fn list_views(
 
 #[tauri::command]
 pub async fn list_functions(
-    state: State<'_, AppState>,
+    state: State<'_, Arc<AppState>>,
     connection_id: String,
     schema: String,
 ) -> TuskResult<Vec<SchemaObject>> {
@@ -155,7 +171,7 @@ pub async fn list_functions(
 
 #[tauri::command]
 pub async fn list_indexes(
-    state: State<'_, AppState>,
+    state: State<'_, Arc<AppState>>,
     connection_id: String,
     schema: String,
 ) -> TuskResult<Vec<SchemaObject>> {
@@ -188,7 +204,7 @@ pub async fn list_indexes(
 
 #[tauri::command]
 pub async fn list_sequences(
-    state: State<'_, AppState>,
+    state: State<'_, Arc<AppState>>,
     connection_id: String,
     schema: String,
 ) -> TuskResult<Vec<SchemaObject>> {
@@ -219,17 +235,16 @@ pub async fn list_sequences(
         .collect())
 }
 
-#[tauri::command]
-pub async fn get_table_columns(
-    state: State<'_, AppState>,
-    connection_id: String,
-    schema: String,
-    table: String,
+pub async fn get_table_columns_core(
+    state: &AppState,
+    connection_id: &str,
+    schema: &str,
+    table: &str,
 ) -> TuskResult<Vec<ColumnInfo>> {
     let pools = state.pools.read().await;
     let pool = pools
-        .get(&connection_id)
-        .ok_or(TuskError::NotConnected(connection_id))?;
+        .get(connection_id)
+        .ok_or_else(|| TuskError::NotConnected(connection_id.to_string()))?;
 
     let rows = sqlx::query(
         "SELECT \
@@ -254,8 +269,8 @@ pub async fn get_table_columns(
          WHERE c.table_schema = $1 AND c.table_name = $2 \
          ORDER BY c.ordinal_position",
     )
-    .bind(&schema)
-    .bind(&table)
+    .bind(schema)
+    .bind(table)
     .fetch_all(pool)
     .await
     .map_err(TuskError::Database)?;
@@ -274,9 +289,19 @@ pub async fn get_table_columns(
         .collect())
 }
 
+#[tauri::command]
+pub async fn get_table_columns(
+    state: State<'_, Arc<AppState>>,
+    connection_id: String,
+    schema: String,
+    table: String,
+) -> TuskResult<Vec<ColumnInfo>> {
+    get_table_columns_core(&state, &connection_id, &schema, &table).await
+}
+
 #[tauri::command]
 pub async fn get_table_constraints(
-    state: State<'_, AppState>,
+    state: State<'_, Arc<AppState>>,
     connection_id: String,
     schema: String,
     table: String,
@@ -317,7 +342,7 @@ pub async fn get_table_constraints(
 
 #[tauri::command]
 pub async fn get_table_indexes(
-    state: State<'_, AppState>,
+    state: State<'_, Arc<AppState>>,
     connection_id: String,
     schema: String,
     table: String,
@@ -359,7 +384,7 @@ pub async fn get_table_indexes(
 
 #[tauri::command]
 pub async fn get_completion_schema(
-    state: State<'_, AppState>,
+    state: State<'_, Arc<AppState>>,
     connection_id: String,
 ) -> TuskResult<HashMap<String, HashMap<String, Vec<String>>>> {
     let pools = state.pools.read().await;
@@ -396,7 +421,7 @@ pub async fn get_completion_schema(
 
 #[tauri::command]
 pub async fn get_column_details(
-    state: State<'_, AppState>,
+    state: State<'_, Arc<AppState>>,
     connection_id: String,
     schema: String,
     table: String,