Add thread section management APIs (#36380)

## What changed

- Add `threadSection/create`, `threadSection/update`, and `threadSection/delete` app-server methods, with generated protocol schemas and TypeScript bindings.
- Persist custom sections in SQLite with stable UUIDv7 identities, trim and validate display names, and prevent renaming or deleting the built-in pinned section.
- Delete sections transactionally and return their active and archived threads to the unsectioned list.
- Serialize section mutations with section listing so concurrent requests observe ordered updates.

## Testing

- Cover section persistence across restarts, ordered renames, member cleanup on deletion, invalid requests, unsupported stores, and thread-store/state-runtime behavior.

GitOrigin-RevId: dc9a4be283c21dbc93ab1829eafc4825d8df6575

codex-rs/thread-store/src/lib.rs

@@ -10,6 +10,7 @@ mod live_thread;
 mod local;
 mod store;
 mod thread_metadata_sync;
+mod thread_sections;
 mod types;
 
 pub use error::ThreadStoreError;
@@ -22,6 +23,12 @@ pub use local::LocalThreadStore;
 pub use local::LocalThreadStoreConfig;
 pub use store::ThreadStore;
 pub use store::ThreadStoreFuture;
+pub use thread_sections::CreateThreadSectionParams;
+pub use thread_sections::DeleteThreadSectionParams;
+pub use thread_sections::ListThreadSectionsParams;
+pub use thread_sections::RenameThreadSectionParams;
+pub use thread_sections::StoredThreadSection;
+pub use thread_sections::StoredThreadSectionsPage;
 pub use types::AppendThreadItemsParams;
 pub use types::ArchiveThreadParams;
 pub use types::ArchiveThreadsParams;