Unify thread metadata updates above store (#22236)

- make ThreadStore::update_thread_metadata accept a broad range of
metadata patches
- keep ThreadStore::append_items as raw canonical history append (no
metadata side effects)
- in the local store, write these metadata updates to a combination of
sqlite and rollout jsonl files for backwards-compat. It special cases
which fields need to go into jsonl vs sqlite vs whatever, confining the
awkwardness to just this implementation
- in remote stores we can simply persist the metadata directly to a
database, no special casing required.
- move the "implicit metadata updates triggered by appending rollout
items" from the RolloutRecorder (which is local-threadstore-specific) to
the LiveThread layer above the ThreadStore, inside of a private helper
utility called ThreadMetadataSync. LiveThread calls ThreadStore
append_items and update_metadata separately.
- Add a generic update metadata method to ThreadManager that works on
both live threads and "cold" threads
- Call that ThreadManager method from app server code, so app server
doesn't need to worry about whether the thread is live or not

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

@@ -9,6 +9,7 @@ mod in_memory;
 mod live_thread;
 mod local;
 mod store;
+mod thread_metadata_sync;
 mod types;
 
 pub use error::ThreadStoreError;
@@ -22,6 +23,7 @@ pub use local::LocalThreadStoreConfig;
 pub use store::ThreadStore;
 pub use types::AppendThreadItemsParams;
 pub use types::ArchiveThreadParams;
+pub use types::ClearableField;
 pub use types::CreateThreadParams;
 pub use types::GitInfoPatch;
 pub use types::ItemPage;
@@ -29,7 +31,6 @@ pub use types::ListItemsParams;
 pub use types::ListThreadsParams;
 pub use types::ListTurnsParams;
 pub use types::LoadThreadHistoryParams;
-pub use types::OptionalStringPatch;
 pub use types::ReadThreadByRolloutPathParams;
 pub use types::ReadThreadParams;
 pub use types::ResumeThreadParams;