feat: unify coordinator semantics (Muse role alignment phase 1)

Platform coordinator.py is the single source of truth; the skill
coordinator template (templates/roles/00-coordinator.md + SKILL.md
appendix 00 + body) now derives from it instead of describing a
second, model-played coordinator (U1-U13).

- server: _create_task accepts parent_task_id (404/400 checks,
  coordinator-under-coordinator rejected); follow-ups to a running
  coordinator return 409 at entry (_create_followup /
  _deliver_to_thread) with documented alternatives (U14/U15).
- tests: 8 new coordinator tests (depth limit, lineage, replay,
  follow-up 409); appendix sync/provenance/transplant suites green.
- check_appendix.py: 12 chapters match templates/roles/.

cloud/server.py

@@ -3812,6 +3812,31 @@ class CloudControlPlaneHandler(OAuthMixin, IdentityMemoryMixin, ProjectMixin, Au
                     "error": "协调员任务不跑模型回合，不能与"
                              " goal/plan/验收命令同用"})
                 return
+        # 父任务血缘（Muse 角色对齐 P1）：创建请求可携带
+        # parent_task_id；父任务是协调员且本次新建也是协调员
+        # 时拒绝（深度恒 ≤1）。父不存在 404、跨项目 400。
+        # 不带 coordinator_parts 时 parent_task_id 仅作血缘记录
+        # （第二阶段旁聊的父子关系用同一入参）。
+        parent_task_id = body.get("parent_task_id")
+        if parent_task_id is not None:
+            if not isinstance(parent_task_id, str):
+                self._send_json(400, {
+                    "error": "parent_task_id must be a string"})
+                return
+            parent_row = self._fetch_task(parent_task_id)
+            if parent_row is None:
+                self._send_json(404, {"error": "parent task not found"})
+                return
+            parent_task = _task_to_dict(parent_row)
+            if parent_task["project_id"] != project_id:
+                self._send_json(400, {
+                    "error": "parent task belongs to another project"})
+                return
+            if coord_parts and parent_task.get("coordinator_parts"):
+                self._send_json(400, {
+                    "error": "coordinator task cannot be created"
+                             " under a coordinator task"})
+                return
         idempotency_key = body.get("idempotency_key")
         if idempotency_key is not None and not isinstance(idempotency_key, str):
             self._send_json(400, {"error": "idempotency_key must be a string"})
@@ -4031,7 +4056,7 @@ class CloudControlPlaneHandler(OAuthMixin, IdentityMemoryMixin, ProjectMixin, Au
                      model, effort, approval, plan, goal_mode,
                      environment_id,
                      json.dumps(coord_parts) if coord_parts else None,
-                     None, None, child_model, child_effort,
+                     parent_task_id, None, child_model, child_effort,
                      agent_name_val, agent_version_val,
                      agent_instructions_val, agent_tools_val,
                      agent_tool_approvals_val, audit_loop_val),
@@ -4440,6 +4465,15 @@ class CloudControlPlaneHandler(OAuthMixin, IdentityMemoryMixin, ProjectMixin, Au
                 return
         if self._reject_if_over_quota_for_task(user_id, task):
             return
+        # 协调员任务不接受后续消息（Muse 角色对齐 P1）：写入侧
+        # 会 201 成功、消费侧没有任何读点，宁可入口 409 明拒。
+        # 改分工请取消后重建协调员；给分工追加指令请直接发给
+        # 该子任务。
+        if task.get("coordinator_parts"):
+            self._send_json(409, {
+                "error": "coordinator tasks do not accept"
+                         " follow-up messages"})
+            return
         text, mode, body_err = _validate_followup_body(body)
         if body_err is not None:
             self._send_json(body_err[0], body_err[1])
@@ -5922,6 +5956,12 @@ class CloudControlPlaneHandler(OAuthMixin, IdentityMemoryMixin, ProjectMixin, Au
         (http_code, payload)，不直接 _send_json；配额检查
         由调用方在调本方法前做。"""
         task_id = task["id"]
+        # 协调员任务不接受后续消息（Muse 角色对齐 P1）：与
+        # _create_followup 同款入口 409，见该处注释。
+        if task.get("coordinator_parts"):
+            return 409, {
+                "error": "coordinator tasks do not accept"
+                         " follow-up messages"}
         goal_target = _parse_goal_command(text)
         # /goal 前置判定见 _classify_goal_followup（纯计算，与
         # _create_followup 共用，但只用于 goal_target 非空时：