Add persisted thread pinning to the app server (#34840)

## What changed

- Add `isPinned` to thread responses and allow `thread/metadata/update` to pin or unpin stored threads.
- Add an `isPinned` filter to `thread/list`, including cursor-based pagination and combinations with relationship filters.
- Persist pin state in SQLite without modifying rollout files, default existing threads to unpinned, and preserve pins through reconciliation and archive transitions.

## Testing

- Cover protocol serialization, database migration and indexing, pin updates, filtered pagination, rollout reconciliation, and archive/unarchive behavior.

GitOrigin-RevId: c2eacabd6dae465e2ae6ce8a169e00740960cdb7

codex-rs/app-server-protocol/src/protocol/v2/tests.rs

@@ -185,6 +185,7 @@ fn thread_resume_response_round_trips_initial_turns_page() {
             parent_thread_id: None,
             preview: String::new(),
             ephemeral: false,
+            is_pinned: true,
             history_mode: Default::default(),
             model_provider: "openai".to_string(),
             created_at: 1,
@@ -225,6 +226,17 @@ fn thread_resume_response_round_trips_initial_turns_page() {
     };
 
     let value = serde_json::to_value(&response).expect("serialize thread resume response");
+    assert_eq!(value["thread"]["isPinned"], json!(true));
+
+    let mut legacy_thread = value["thread"].clone();
+    legacy_thread
+        .as_object_mut()
+        .expect("serialized thread should be an object")
+        .remove("isPinned");
+    let legacy_thread =
+        serde_json::from_value::<Thread>(legacy_thread).expect("deserialize legacy thread");
+    assert!(!legacy_thread.is_pinned);
+
     assert_eq!(
         value.get("initialTurnsPage"),
         Some(&json!({
@@ -356,6 +368,42 @@ fn thread_list_params_accepts_state_db_only_flag() {
     assert!(params.use_state_db_only);
 }
 
+#[test]
+fn thread_list_params_accepts_pinned_filter() {
+    for is_pinned in [true, false] {
+        let params = serde_json::from_value::<ThreadListParams>(json!({
+            "isPinned": is_pinned,
+        }))
+        .expect("pinned filter should deserialize");
+
+        assert_eq!(params.is_pinned, Some(is_pinned));
+    }
+
+    let params = serde_json::from_value::<ThreadListParams>(json!({}))
+        .expect("omitted pinned filter should deserialize");
+    assert_eq!(params.is_pinned, None);
+}
+
+#[test]
+fn thread_metadata_update_params_accepts_pinned_patch() {
+    for is_pinned in [true, false] {
+        let params = serde_json::from_value::<ThreadMetadataUpdateParams>(json!({
+            "threadId": "thr_123",
+            "isPinned": is_pinned,
+        }))
+        .expect("pinned metadata patch should deserialize");
+
+        assert_eq!(params.is_pinned, Some(is_pinned));
+        assert_eq!(params.git_info, None);
+    }
+
+    let params = serde_json::from_value::<ThreadMetadataUpdateParams>(json!({
+        "threadId": "thr_123",
+    }))
+    .expect("omitted pinned metadata patch should deserialize");
+    assert_eq!(params.is_pinned, None);
+}
+
 #[test]
 fn collab_agent_state_maps_interrupted_status() {
     assert_eq!(