feat(engine): the manager — chat orders, team, triage, verdicts, bootstrap

Phase 3 of the AI-workforce engine (TODO-agent-2):

- engine/manager.py: ManagerTurns.chat (CREATE_TASK/PAUSE/RESUME/CANCEL,
  HIRE/UPDATE_EMPLOYEE/FIRE, KNOWLEDGE), triage (ASSIGN/REJECT/ASK_USER),
  final_review (COMPLETE/REVISE +cycle), error_review (RESOLVE_ERROR/CANCEL),
  bootstrap_team; post_user_message now delegates to it.
- One billing path: call_model/BillingScope in runner.py is the single model
  entry point (fixes the agybot chat-billing bug).
- Team changes capped at 3/turn, employee cap, last manager cannot be fired,
  hires pick a granted model of the requested tier strictly.
- container_engine.py wires the real WorkforceBootstrapPort.
- Fixes: REVISE is a body tag (prompt and parser now agree); ASSIGN
  employee="" means pick-for-me; the runner's protocol-error retry is capped by
  engine_max_protocol_retries (was unbounded until the turn timeout).
- 20 new manager tests + regression tests; report in
  docs/plan/reports/agent-2-phase-3.md.

apps/api/app/application/engine/protocol.py

@@ -104,6 +104,7 @@ BODY_TAGS: frozenset[TagName] = frozenset(
         TagName.EDIT_FILE,
         TagName.KNOWLEDGE,
         TagName.ASK_USER,
+        TagName.REVISE,
         TagName.CREATE_TASK,
         TagName.SPLIT,
         TagName.PLAN_SPEC,
@@ -282,14 +283,15 @@ _EDIT_BLOCK_RE = re.compile(
 def assign_of(tag: Tag) -> AssignTag:
     """Read an ``ASSIGN`` tag. ``employee=""`` means "pick for me"."""
     employee = tag.attr("employee", "").strip()
-    if not employee and not tag.attr("task_id", "").strip():
+    task_id = tag.attr("task_id", "").strip()
+    # ``employee=""`` is a deliberate "pick the least busy one"; a tag with
+    # neither attribute at all is a mistake we quote back to the model.
+    if "employee" not in tag.attrs and "task_id" not in tag.attrs:
         raise ProtocolError("[[ASSIGN]] needs employee=... or task_id=...")
     pipeline = tag.attr("pipeline", "").strip()
     if pipeline and pipeline not in ASSIGNABLE_PIPELINES:
         raise ProtocolError(f"unknown pipeline: {pipeline}")
-    return AssignTag(
-        employee=employee, pipeline=pipeline, task_id=tag.attr("task_id", "").strip()
-    )
+    return AssignTag(employee=employee, pipeline=pipeline, task_id=task_id)
 
 
 def task_draft_of(tag: Tag) -> TaskDraft: