fix(gateway): thread agent_team through all 27 lifecycle Context sites

Arms the team-match spec gate that sat in its permissive fallback since
shipping: cell-scoped roles are now rejected on cross-team verbs at the
gateway (a misrouted frontend PM blocked, escalated, and held a backend
task live 2026-07-02). Org-wide roles remain exempt via the policy-side
_ORG_WIDE_ROLES. Test mocks aligned to carry consistent teams.

tests/unit/gateway/test_claim_arg_order.py

@@ -277,6 +277,7 @@ async def test_i_will_plan_calls_claim_and_start_with_task_id_first() -> None:
         status="pending",
         plan=None,
         assigned_to=None,
+        team="backend",
         task_type="planning",
         parent_task_id=None,
         sequence=0,