Leverage state DB metadata for thread summaries (#10621)

Summary:
- read conversation summaries and cwd info from the state DB when
possible so we no longer rely on rollout files for metadata and avoid
extra I/O
- persist CLI version in thread metadata, surface it through summary
builders, and add the necessary DB migration hooks
- simplify thread listing by using enriched state DB data directly
rather than reading rollout heads

Testing:
- Not run (not requested)

codex-rs/state/migrations/0007_threads_first_user_message.sql

@@ -0,0 +1,5 @@
+ALTER TABLE threads ADD COLUMN first_user_message TEXT NOT NULL DEFAULT '';
+
+UPDATE threads
+SET first_user_message = title
+WHERE first_user_message = '' AND has_user_event = 1 AND title <> '';