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/cli_stream.rs

@@ -85,13 +85,8 @@ async fn responses_mode_stream_cli() {
         !page.items.is_empty(),
         "expected at least one session to be listed"
     );
-    // First line of head must be the SessionMeta payload (id/timestamp)
-    let head0 = page.items[0].head.first().expect("missing head record");
-    assert!(head0.get("id").is_some(), "head[0] missing id");
-    assert!(
-        head0.get("timestamp").is_some(),
-        "head[0] missing timestamp"
-    );
+    assert!(page.items[0].thread_id.is_some(), "missing thread_id");
+    assert!(page.items[0].created_at.is_some(), "missing created_at");
 }
 
 /// Verify that passing `-c model_instructions_file=...` to the CLI