Stop sidecar process when the app exits

The sidecar process was orphaned when the Tauri app closed, leaving
ports 8080/8081 in use. On next launch the new sidecar couldn't bind
those ports and failed to start.

Added RunEvent::Exit handler that stops the sidecar before the app
process terminates.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src-tauri/src/lib.rs

@@ -71,6 +71,17 @@ pub fn run() {
             sidecar::reset_sidecar,
             write_log,
         ])
-        .run(tauri::generate_context!())
+        .build(tauri::generate_context!())
-        .expect("error while running tauri application");
+        .expect("error while building tauri application")
+        .run(|app, event| {
+            if let tauri::RunEvent::Exit = event {
+                // Stop the sidecar when the app exits
+                if let Some(state) = app.try_state::<sidecar::ManagedSidecar>() {
+                    if let Ok(mut mgr) = state.0.lock() {
+                        eprintln!("[app] Stopping sidecar on exit...");
+                        mgr.stop();
+                    }
+                }
+            }
+        });
 }