feat(memory): capture user_id at enqueue time for async-safe thread isolation

Add user_id field to ConversationContext and MemoryUpdateQueue.add() so the
user identity is stored explicitly at request time, before threading.Timer
fires on a different thread where ContextVar values do not propagate.
MemoryMiddleware.after_agent() now calls get_effective_user_id() at enqueue
time and passes the value through to updater.update_memory().

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/packages/harness/deerflow/agents/memory/queue.py

@@ -20,6 +20,7 @@ class ConversationContext:
     messages: list[Any]
     timestamp: datetime = field(default_factory=lambda: datetime.now(UTC))
     agent_name: str | None = None
+    user_id: str | None = None
     correction_detected: bool = False
     reinforcement_detected: bool = False
 
@@ -44,6 +45,7 @@ class MemoryUpdateQueue:
         thread_id: str,
         messages: list[Any],
         agent_name: str | None = None,
+        user_id: str | None = None,
         correction_detected: bool = False,
         reinforcement_detected: bool = False,
     ) -> None:
@@ -53,6 +55,9 @@ class MemoryUpdateQueue:
             thread_id: The thread ID.
             messages: The conversation messages.
             agent_name: If provided, memory is stored per-agent. If None, uses global memory.
+            user_id: The user ID captured at enqueue time. Stored in ConversationContext so it
+                survives the threading.Timer boundary (ContextVar does not propagate across
+                raw threads).
             correction_detected: Whether recent turns include an explicit correction signal.
             reinforcement_detected: Whether recent turns include a positive reinforcement signal.
         """
@@ -71,6 +76,7 @@ class MemoryUpdateQueue:
                 thread_id=thread_id,
                 messages=messages,
                 agent_name=agent_name,
+                user_id=user_id,
                 correction_detected=merged_correction_detected,
                 reinforcement_detected=merged_reinforcement_detected,
             )
@@ -136,6 +142,7 @@ class MemoryUpdateQueue:
                         agent_name=context.agent_name,
                         correction_detected=context.correction_detected,
                         reinforcement_detected=context.reinforcement_detected,
+                        user_id=context.user_id,
                     )
                     if success:
                         logger.info("Memory updated successfully for thread %s", context.thread_id)