fix(calendar): read agent status by agent_id alone (cross-agent gate)

GET /calendar/agent/status went through _require_agent, which filters by
agent_id AND claw_identifier. But this is a cross-agent READ — the caller asks
about a DIFFERENT agent and passes its OWN X-Claw-Identifier (the CLI falls
back to hostname). So the query required target.claw == caller's-hostname and
spuriously 404'd whenever they differed: `hf agent status-of <other>` worked
only when the caller's host happened to equal the target's registered claw
(e.g. fine on the node whose hostname matched, 404 everywhere else). This broke
the delegate-task / on-call-handoff status gates.

Look the agent up by agent_id alone for the read; accept but ignore
X-Claw-Identifier (now optional). The POST (write own status) still identifies
the caller by agent_id + claw via _require_agent.

Verified: `hf agent status-of <agent>` now returns {agent_id, status} from any
caller/host; unknown agent still 404s.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/api/routers/calendar.py

@@ -568,17 +568,28 @@ def agent_update_virtual_slot(
 )
 def get_agent_status(
     agent_id: str = Query(..., description="Target agent_id"),
-    x_claw_identifier: str = Header(..., alias="X-Claw-Identifier"),
+    x_claw_identifier: str = Header(None, alias="X-Claw-Identifier"),
     db: Session = Depends(get_db),
 ):
     """Return `{agent_id, status}` so callers (Fabric.OpenclawPlugin's
-    triage on-call gate, etc.) can decide whether the agent is currently
-    eligible without flipping their state.
+    triage on-call gate, delegate-task / on-call-handoff status gates, etc.)
+    can decide whether the agent is currently eligible without flipping
+    their state.
+
+    This is a cross-agent READ: look the agent up by `agent_id` ALONE. We do
+    NOT scope by the caller's claw_identifier — the caller is asking about a
+    DIFFERENT agent, and the X-Claw-Identifier the CLI sends is the caller's
+    own (often just a hostname fallback), so requiring target.claw == that
+    header spuriously 404'd whenever the two claws differed (e.g. any
+    `hf agent status-of` from a host whose hostname != the target's
+    registered claw). The header is accepted but ignored.
 
     No-op for unknown agents — returns 404 with `{detail: 'Agent not
     found'}` so the caller can decide whether to fail-open or fail-closed.
     """
-    agent = _require_agent(db, agent_id, x_claw_identifier)
+    agent = db.query(Agent).filter(Agent.agent_id == agent_id).first()
+    if agent is None:
+        raise HTTPException(status_code=404, detail="Agent not found")
     return {
         "agent_id": agent.agent_id,
         "status": agent.status.value if hasattr(agent.status, 'value') else str(agent.status),