fix: stamp timestamps in model_metadata, turn_finalizer

agent/turn_finalizer.py

@@ -26,6 +26,7 @@ import os
 
 from agent.codex_responses_adapter import _summarize_user_message_for_log
 from agent.message_content import flatten_message_text
+from agent.message_metadata import append_message, stamp_message_timestamp
 from agent.message_sanitization import _sanitize_surrogates
 
 
@@ -315,7 +316,10 @@ def finalize_turn(
             if _tail_role != "assistant":
                 # Tail is not an assistant row — append the final response
                 # so the durable turn closes with the answer (#43849/#44100).
-                messages.append({"role": "assistant", "content": final_response})
+                append_message(
+                    messages,
+                    {"role": "assistant", "content": final_response},
+                )
             elif isinstance(_tail, dict) and _tail.get("content") != final_response and _is_pure_tool_call_tail(_tail):
                 # The tail IS an assistant row, but a *pure tool-call turn*:
                 # tool_calls with no text of its own. The role check alone
@@ -332,6 +336,10 @@ def finalize_turn(
                 # candidate collapse — the provisional answer was persisted and
                 # reused as the terminal response, #65919 §7).
                 _tail["content"] = final_response
+                # The normal assistant builder already stamps this row. Cover
+                # legacy/exceptional pure-tool tails before they become a
+                # delivered final response.
+                stamp_message_timestamp(_tail)
                 # The row may have already been flushed to SQLite by the
                 # incremental tool-call persist (conversation_loop.py:4990),
                 # which stamps ``_DB_PERSISTED_MARKER`` so subsequent flushes