Add app-server thread/delete API (#25018)

## Why

Clients can archive and unarchive threads today, but there is no
app-server API for permanently removing a thread. Deletion also needs to
cover the full session tree: deleting a main thread should remove
spawned subagent threads and the related local metadata instead of
leaving orphaned rollout files, goals, or subagent state behind.

## What

- Adds the v2 `thread/delete` request and `thread/deleted` notification,
with the response shape kept consistent with `thread/archive`.
- Implements local hard delete for active and archived rollout files.
- Deletes the requested thread's state DB row as the commit point, then
best-effort cleans associated state including spawned descendants,
goals, spawn edges, logs, dynamic tools, and agent job assignments.
- Updates app-server API docs and generated protocol schema/TypeScript
fixtures.

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

@@ -400,7 +400,7 @@ impl MessageProcessor {
             Arc::clone(&thread_manager),
             Arc::clone(&config),
             feedback,
-            log_db,
+            log_db.clone(),
             state_db.clone(),
         );
         let git_processor = GitRequestProcessor::new();
@@ -454,6 +454,7 @@ impl MessageProcessor {
             Arc::clone(&thread_list_state_permit),
             thread_goal_processor.clone(),
             state_db,
+            log_db,
             Arc::clone(&skills_watcher),
         );
         let turn_processor = TurnRequestProcessor::new(
@@ -1071,6 +1072,11 @@ impl MessageProcessor {
                     .thread_archive(request_id.clone(), params)
                     .await
             }
+            ClientRequest::ThreadDelete { params, .. } => {
+                self.thread_processor
+                    .thread_delete(request_id.clone(), params)
+                    .await
+            }
             ClientRequest::ThreadIncrementElicitation { params, .. } => {
                 self.thread_processor
                     .thread_increment_elicitation(params)