codex: move unloaded thread writes into store (#18361)

- Migrates unloaded `thread/name/set` and `thread/memoryModeSet`
app-server writes behind the generic
`ThreadStore::update_thread_metadata` API rather than adding one-off
store methods for setting thread name or memory mode.
- Implements the local ThreadStore metadata patch path for thread name
and memory mode, including rollout append, legacy name index updates,
SessionMeta validation/update, SQLite reconciliation, and re-reading the
stored thread.
- Adds focused local thread-store unit coverage plus app-server
integration coverage for the migrated unloaded write paths.

codex-rs/thread-store/src/local/mod.rs

@@ -3,6 +3,7 @@ mod helpers;
 mod list_threads;
 mod read_thread;
 mod unarchive_thread;
+mod update_thread_metadata;
 
 #[cfg(test)]
 mod test_support;
@@ -17,7 +18,6 @@ use crate::ListThreadsParams;
 use crate::LoadThreadHistoryParams;
 use crate::ReadThreadParams;
 use crate::ResumeThreadRecorderParams;
-use crate::SetThreadNameParams;
 use crate::StoredThread;
 use crate::StoredThreadHistory;
 use crate::ThreadPage;
@@ -75,15 +75,11 @@ impl ThreadStore for LocalThreadStore {
         list_threads::list_threads(self, params).await
     }
 
-    async fn set_thread_name(&self, _params: SetThreadNameParams) -> ThreadStoreResult<()> {
-        unsupported("set_thread_name")
-    }
-
     async fn update_thread_metadata(
         &self,
-        _params: UpdateThreadMetadataParams,
+        params: UpdateThreadMetadataParams,
     ) -> ThreadStoreResult<StoredThread> {
-        unsupported("update_thread_metadata")
+        update_thread_metadata::update_thread_metadata(self, params).await
     }
 
     async fn archive_thread(&self, params: ArchiveThreadParams) -> ThreadStoreResult<()> {