Deprecate full-history hydration for paginated threads (#40676)

## Why

Paginated thread history should be loaded incrementally through
`thread/turns/list` and `thread/items/list` instead of being fully reconstructed
in `thread.turns`.

## What changed

- Emit `deprecationNotice` when `thread/read`, `thread/resume`, or `thread/fork`
  requests full history for a paginated thread.
- Direct clients to omit `includeTurns` for reads or use `excludeTurns: true` for
  resumes and forks, then page history through the list APIs.
- Document the deprecation in the protocol schemas and app-server README.

## Testing

- Cover notices for paginated reads, cold and loaded resumes, and forks.
- Verify metadata-only requests, legacy threads, and rejected forks do not emit
  the notice.

GitOrigin-RevId: 0d387b46d73608f90b7960120a54af4ef332e510

codex-rs/app-server/src/message_processor.rs

@@ -1329,7 +1329,7 @@ impl MessageProcessor {
                 self.thread_processor.thread_loaded_list(params).await
             }
             ClientRequest::ThreadRead { params, .. } => {
-                self.thread_processor.thread_read(params).await
+                self.thread_processor.thread_read(&request_id, params).await
             }
             ClientRequest::ThreadTurnsList { params, .. } => {
                 self.thread_processor.thread_turns_list(params).await