[codex] Add local thread store listing (#17824)

Builds on top of #17659 

Move the filesystem + sqlite thread listing-related operations inside of
a local ThreadStore implementation and call ThreadStore from the places
that used to perform these filesystem/sqlite operations.

This is the first of a series of PRs that will implement the rest of the
local ThreadStore.

Testing:
- added unit tests for the thread store implementation
- adjusted some unit tests in the realtime + personality packages whose
callsites changed. Specifically I'm trying to hide ThreadMetadata inside
of the local implementation and make ThreadMetadata a sqlite
implementation detail concern rather than a public interface, preferring
the more generate StoredThread interface instead
- added a corner case test for the personality migration package that
wasn't covered by the existing test suite
- adjust the behavior of searched thread listing to run the existing
local rollout repair/backfill pass _before_ querying SQLite results, so
callers using ThreadStore::list_threads do not miss matches after a
partial metadata warm-up

codex-rs/core/src/codex_tests.rs

@@ -2836,6 +2836,9 @@ pub(crate) async fn make_session_and_context() -> (Session, TurnContext) {
         network_proxy: None,
         network_approval: Arc::clone(&network_approval),
         state_db: None,
+        thread_store: codex_thread_store::LocalThreadStore::new(
+            codex_rollout::RolloutConfig::from_view(config.as_ref()),
+        ),
         model_client: ModelClient::new(
             Some(auth_manager.clone()),
             conversation_id,
@@ -3693,6 +3696,9 @@ pub(crate) async fn make_session_and_context_with_dynamic_tools_and_rx(
         network_proxy: None,
         network_approval: Arc::clone(&network_approval),
         state_db: None,
+        thread_store: codex_thread_store::LocalThreadStore::new(
+            codex_rollout::RolloutConfig::from_view(config.as_ref()),
+        ),
         model_client: ModelClient::new(
             Some(Arc::clone(&auth_manager)),
             conversation_id,