[chore] logical-gaps: verb_runner trailing-None side-effect guard + actor_agent_id threading (3 gaps)

_verb_runner.py:
- run_intent skips the side_effects loop when a TRAILING composed action
  returned None (its source-status check failed under a concurrent
  transition). Previously the loop ran unconditionally on the None task
  and _do_push_branch(None)/_do_pr_merge(None) crashed with a
  NoneType AttributeError, turning the clean INVALID_STATE the
  entry/intermediate guards give into a 500/respawn loop. The trailing
  None now flows to the caller's `if task is None` handler. Latent today
  (no shipped intent has both a None-capable compose and trailing
  side_effects) but the runner is generic. (gap: runner-side-effects-fire-
  on-trailing-none-task)
- _do_push_branch / _do_create_pr / _do_create_root_pr forward
  actor_agent_id=agent.id into git_service (push_branch / create_pr),
  matching _do_pr_merge. Without it, a verb on a task whose assigned_to
  was cleared before the side effect falls through to created_by and
  pushes from / opens a PR against the wrong workspace.
  (gap: side-effect-handlers-drop-actor-agent-id)
- _do_escalate_to_ceo forwards actor_agent_id=agent.id so the
  awaiting_ceo_approval audit row attributes to the specific PM/Board
  agent. (gap: do-escalate-to-ceo-drops-actor-agent-id)

task.py: escalate_to_ceo gains actor_agent_id param, passed as
audit_agent_id to _validate_and_set_status and recorded as
escalated_by_agent_id in the event payload + log. escalate_to_ceo_for_agent
forwards agent.agent_id.

_impl.py: the main_pm complete->escalate path forwards
actor_agent_id=main_pm_agent_id.

TDD: 5 red->green tests (synthetic trailing-None intent, actor forwarding
for push_branch/create_pr/create_root_pr/escalate_to_ceo) + real-DB audit
test asserting the awaiting_ceo_approval row carries the actor UUID.
Updated 3 board escalate_to_ceo tests to assert the forwarded actor.

tests/unit/gateway/test_choreographer_board.py

@@ -72,7 +72,7 @@ async def test_board_escalate_to_ceo_succeeds_for_product_owner() -> None:
     after = MagicMock(**{**t.__dict__, "status": "awaiting_ceo_approval"})
     task_svc = AsyncMock()
     task_svc.get.return_value = t
-    task_svc.agent_for.return_value = MagicMock(role="product_owner")
+    task_svc.agent_for.return_value = MagicMock(id=agent_id, role="product_owner")
     task_svc.escalate_to_ceo.return_value = after
     journal_svc = AsyncMock()
     journal_svc.has_decision_for_task.return_value = True
@@ -87,6 +87,7 @@ async def test_board_escalate_to_ceo_succeeds_for_product_owner() -> None:
         task_id=task_id,
         agent_role="product_owner",
         notes="ready for CEO sign-off",
+        actor_agent_id=agent_id,
     )
 
 
@@ -102,7 +103,7 @@ async def test_board_escalate_to_ceo_succeeds_for_head_marketing() -> None:
     after = MagicMock(**{**t.__dict__, "status": "awaiting_ceo_approval"})
     task_svc = AsyncMock()
     task_svc.get.return_value = t
-    task_svc.agent_for.return_value = MagicMock(role="head_marketing")
+    task_svc.agent_for.return_value = MagicMock(id=agent_id, role="head_marketing")
     task_svc.escalate_to_ceo.return_value = after
     journal_svc = AsyncMock()
     journal_svc.has_decision_for_task.return_value = True
@@ -117,6 +118,7 @@ async def test_board_escalate_to_ceo_succeeds_for_head_marketing() -> None:
         task_id=task_id,
         agent_role="head_marketing",
         notes="brand-affecting change",
+        actor_agent_id=agent_id,
     )
 
 
@@ -236,7 +238,7 @@ async def test_board_escalate_to_ceo_succeeds_for_main_pm() -> None:
     after = MagicMock(**{**t.__dict__, "status": "awaiting_ceo_approval"})
     task_svc = AsyncMock()
     task_svc.get.return_value = t
-    task_svc.agent_for.return_value = MagicMock(role="main_pm")
+    task_svc.agent_for.return_value = MagicMock(id=agent_id, role="main_pm")
     task_svc.escalate_to_ceo.return_value = after
     journal_svc = AsyncMock()
     journal_svc.has_decision_for_task.return_value = True
@@ -251,6 +253,7 @@ async def test_board_escalate_to_ceo_succeeds_for_main_pm() -> None:
         task_id=task_id,
         agent_role="main_pm",
         notes="root task done",
+        actor_agent_id=agent_id,
     )