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.

crates/ide-agent/src/lib.rs

@@ -760,6 +760,26 @@ impl AgentManager {
         Ok(())
     }
 
+    /// Returns an archived task to the active list without starting the agent.
+    pub fn unarchive(&self, id: &str) -> IdeResult<()> {
+        let task = self.task(id)?;
+        {
+            let mut s = task.state.lock();
+            if s.task.status != AgentStatus::Archived {
+                return Ok(());
+            }
+            if s.busy {
+                return Err(IdeError::invalid("the task is still stopping"));
+            }
+            s.task.status = AgentStatus::Ready;
+            s.task.error = None;
+            s.task.updated_ms = now_ms();
+        }
+        task.persist();
+        task.emit_task();
+        Ok(())
+    }
+
     /// Forgets the task; with `remove_worktree` also deletes its worktree (the branch stays).
     pub async fn delete(&self, id: &str, remove_worktree: bool) -> IdeResult<()> {
         let task = self.task(id)?;

crates/ide-agent/src/tests.rs

@@ -817,3 +817,36 @@ async fn cursor_approval_choice_applies_before_first_prompt() {
     wait_for(&mgr, &task.id, AgentStatus::Ready).await;
     mgr.shutdown();
 }
+
+#[tokio::test(flavor = "multi_thread")]
+async fn archived_tasks_can_be_restored_and_continue_their_session() {
+    let tmp = tempfile::tempdir().unwrap();
+    let agent = Arc::new(FakeAgent::default());
+    let mgr = manager(tmp.path(), agent.clone());
+    let task = mgr
+        .create(NewAgentTask {
+            prompt: text("again"),
+            provider: "claude".into(),
+            config: vec![],
+            isolation: Isolation::Local,
+            base: None,
+        })
+        .await
+        .unwrap();
+    wait_for(&mgr, &task.id, AgentStatus::Ready).await;
+    let entries = mgr.entries(&task.id, None).unwrap();
+    mgr.archive(&task.id).unwrap();
+    assert!(mgr.prompt(&task.id, text("again"), false).await.is_err());
+    mgr.unarchive(&task.id).unwrap();
+    assert_eq!(mgr.task(&task.id).unwrap().state.lock().task.status, AgentStatus::Ready);
+    assert!(mgr.task(&task.id).unwrap().live.lock().is_none());
+    assert_eq!(mgr.entries(&task.id, None).unwrap().len(), entries.len());
+    drop(mgr);
+    let mgr = manager(tmp.path(), agent.clone());
+    assert_eq!(mgr.task(&task.id).unwrap().state.lock().task.status, AgentStatus::Ready);
+    mgr.prompt(&task.id, text("again"), false).await.unwrap();
+    wait_for(&mgr, &task.id, AgentStatus::Ready).await;
+    assert!(agent.calls.lock().iter().any(|call| call == "session/load"));
+    assert_eq!(mgr.entries(&task.id, None).unwrap().len(), entries.len() + 2);
+    mgr.unarchive(&task.id).unwrap();
+}