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/core/tests/suite/sqlite_state.rs

@@ -169,7 +169,7 @@ async fn backfill_scans_existing_rollouts() -> Result<()> {
     assert_eq!(metadata.id, thread_id);
     assert_eq!(metadata.rollout_path, rollout_path);
     assert_eq!(metadata.model_provider, default_provider);
-    assert!(metadata.has_user_event);
+    assert!(metadata.first_user_message.is_some());
 
     let mut stored_tools = None;
     for _ in 0..40 {
@@ -221,7 +221,7 @@ async fn user_messages_persist_in_state_db() -> Result<()> {
         metadata = db.get_thread(thread_id).await?;
         if metadata
             .as_ref()
-            .map(|entry| entry.has_user_event)
+            .map(|entry| entry.first_user_message.is_some())
             .unwrap_or(false)
         {
             break;
@@ -230,7 +230,7 @@ async fn user_messages_persist_in_state_db() -> Result<()> {
     }
 
     let metadata = metadata.expect("thread should exist in state db");
-    assert!(metadata.has_user_event);
+    assert!(metadata.first_user_message.is_some());
 
     Ok(())
 }