feat(v2): add SidecarManager and agent Tauri commands

Implement Rust SidecarManager that spawns Node.js sidecar process,
communicates via stdio NDJSON, and manages agent session lifecycle.
Add agent_query, agent_stop, agent_ready Tauri commands. Sidecar
auto-starts on app launch.

v2/src-tauri/src/lib.rs

@@ -4,13 +4,17 @@ mod watcher;
 mod session;
 
 use pty::{PtyManager, PtyOptions};
+use sidecar::{AgentQueryOptions, SidecarManager};
 use std::sync::Arc;
 use tauri::State;
 
 struct AppState {
     pty_manager: Arc<PtyManager>,
+    sidecar_manager: Arc<SidecarManager>,
 }
 
+// --- PTY commands ---
+
 #[tauri::command]
 fn pty_spawn(
     app: tauri::AppHandle,
@@ -40,10 +44,34 @@ fn pty_kill(state: State<'_, AppState>, id: String) -> Result<(), String> {
     state.pty_manager.kill(&id)
 }
 
+// --- Agent/sidecar commands ---
+
+#[tauri::command]
+fn agent_query(
+    state: State<'_, AppState>,
+    options: AgentQueryOptions,
+) -> Result<(), String> {
+    state.sidecar_manager.query(&options)
+}
+
+#[tauri::command]
+fn agent_stop(state: State<'_, AppState>, session_id: String) -> Result<(), String> {
+    state.sidecar_manager.stop_session(&session_id)
+}
+
+#[tauri::command]
+fn agent_ready(state: State<'_, AppState>) -> bool {
+    state.sidecar_manager.is_ready()
+}
+
 #[cfg_attr(mobile, tauri::mobile_entry_point)]
 pub fn run() {
+    let pty_manager = Arc::new(PtyManager::new());
+    let sidecar_manager = Arc::new(SidecarManager::new());
+
     let app_state = AppState {
-        pty_manager: Arc::new(PtyManager::new()),
+        pty_manager,
+        sidecar_manager: sidecar_manager.clone(),
     };
 
     tauri::Builder::default()
@@ -53,8 +81,11 @@ pub fn run() {
             pty_write,
             pty_resize,
             pty_kill,
+            agent_query,
+            agent_stop,
+            agent_ready,
         ])
-        .setup(|app| {
+        .setup(move |app| {
             if cfg!(debug_assertions) {
                 app.handle().plugin(
                     tauri_plugin_log::Builder::default()
@@ -62,6 +93,13 @@ pub fn run() {
                         .build(),
                 )?;
             }
+
+            // Start sidecar on app launch
+            match sidecar_manager.start(app.handle()) {
+                Ok(()) => log::info!("Sidecar startup initiated"),
+                Err(e) => log::warn!("Sidecar startup failed (agent features unavailable): {e}"),
+            }
+
             Ok(())
         })
         .run(tauri::generate_context!())