feat(app-server): thread/read API (#9569)

codex-rs/app-server/README.md

@@ -79,6 +79,7 @@ Example (from OpenAI's official VSCode extension):
 - `thread/fork` — fork an existing thread into a new thread id by copying the stored history; emits `thread/started` and auto-subscribes you to turn/item events for the new thread.
 - `thread/list` — page through stored rollouts; supports cursor-based pagination and optional `modelProviders` filtering.
 - `thread/loaded/list` — list the thread ids currently loaded in memory.
+- `thread/read` — read a stored thread by id without resuming it; optionally include turns via `includeTurns`.
 - `thread/archive` — move a thread’s rollout file into the archived directory; returns `{}` on success.
 - `thread/rollback` — drop the last N turns from the agent’s in-memory context and persist a rollback marker in the rollout so future resumes see the pruned history; returns the updated `thread` (with `turns` populated) on success.
 - `turn/start` — add user input to a thread and begin Codex generation; responds with the initial `turn` object and streams `turn/started`, `item/*`, and `turn/completed` notifications.
@@ -178,6 +179,20 @@ When `nextCursor` is `null`, you’ve reached the final page.
 } }
 ```
 
+### Example: Read a thread
+
+Use `thread/read` to fetch a stored thread by id without resuming it. Pass `includeTurns` when you want the rollout history loaded into `thread.turns`.
+
+```json
+{ "method": "thread/read", "id": 22, "params": { "threadId": "thr_123" } }
+{ "id": 22, "result": { "thread": { "id": "thr_123", "turns": [] } } }
+```
+
+```json
+{ "method": "thread/read", "id": 23, "params": { "threadId": "thr_123", "includeTurns": true } }
+{ "id": 23, "result": { "thread": { "id": "thr_123", "turns": [ ... ] } } }
+```
+
 ### Example: Archive a thread
 
 Use `thread/archive` to move the persisted rollout (stored as a JSONL file on disk) into the archived sessions directory.