fix(acp): use refresh moment as updated_at on session info push

Follow-up to #26543. The sessions table does not have an updated_at
column (see hermes_state.py — only started_at/ended_at), so
row.get('updated_at') always returned None and the str() coercion was
dead code. Use datetime.now(UTC).isoformat() instead, which reflects
exactly what the field means here: 'the title was refreshed at this
moment'. Drop the dead coercion.

acp_adapter/server.py

@@ -3,6 +3,7 @@
 from __future__ import annotations
 
 import asyncio
+from datetime import datetime, timezone
 import base64
 import contextvars
 import json
@@ -721,9 +722,11 @@ class HermesACPAgent(acp.Agent):
             return
 
         title = row.get("title")
-        updated_at = row.get("updated_at")
+        # The `sessions` table does not have an `updated_at` column (see
-        if updated_at is not None and not isinstance(updated_at, str):
+        # hermes_state.py schema — only started_at/ended_at). Use "now" as
-            updated_at = str(updated_at)
+        # the updated_at since we're emitting this notification precisely
+        # because the title was just refreshed.
+        updated_at = datetime.now(timezone.utc).isoformat()
         update = SessionInfoUpdate(
             session_update="session_info_update",
             title=title if isinstance(title, str) and title.strip() else None,