fix(agents): restore archived tasks for continued conversation (#349)

Archived agent tasks could be opened but never returned to the active list, so their message composer stayed disabled. Unarchive is now available in the task header, in the archived-task notice above the composer, and in the task context menu (including mixed bulk selections). Restoring a task moves it back to the active list, keeps its conversation and worktree, and reconnects the existing agent session on the next message; the backend persists and broadcasts the restored status and refuses restoration while a stopped turn is still settling.

src-tauri/src/commands/agent.rs

@@ -218,6 +218,12 @@ pub fn agent_archive(window: Window, state: State<'_, AppState>, task: String) -
     agent::archive(&state.host, window.label(), task)
 }
 
+#[tauri::command]
+#[specta::specta]
+pub fn agent_unarchive(window: Window, state: State<'_, AppState>, task: String) -> IdeResult<()> {
+    agent::unarchive(&state.host, window.label(), task)
+}
+
 #[tauri::command]
 #[specta::specta]
 pub async fn agent_delete(

src-tauri/src/commands/mod.rs

@@ -94,6 +94,7 @@ pub fn builder() -> tauri_specta::Builder<tauri::Wry> {
         agent::agent_cancel,
         agent::agent_respond,
         agent::agent_archive,
+        agent::agent_unarchive,
         agent::agent_delete,
         agent::agent_changes,
         agent::agent_base_text,