feat: side-thread task kind (Muse role alignment phase 2)

Tasks gain kind='main'|'side' (NULL=main). A side thread hangs under a
parent task, defaults to the local executor, never builds a worktree,
branch or container unless explicitly asked, and writes its conclusion
back to the parent via task_followups on terminal transition.

- server: kind validation + side-thread gates (parent required, no
  coordinator_parts/upload_id/environment_id, parent must not be a
  coordinator), local executor default, GET /tasks kind filter,
  /worktree 404 and /fork /merge /pr 409 for side threads.
- worker: side-default shunt in _run_attempt (no-worktree scratch cwd,
  in-memory plan=1 when a repo is present, seed/checkpoint skipped),
  _writeback_side_thread, marker task-create kind field + inheritance,
  side threads excluded from marker spawn counts.
- host/sandbox: --no-worktree plumbing for dispatch/goal/popen
  (Local + Docker), scratch cwd work/side-threads/<task-id>.
- console (classic only): kind filter + [旁聊] rows + '开旁聊' entry,
  side-thread dispatch mode, side-thread list in detail, merge/PR/fork
  hidden for side threads; build exit 0, console.html sha df39db5a.
- tests: new test_sidethread.py (29 tests) + kind backfill tests in
  test_p2_migrations.py; full cloud suite 3900 tests OK (skipped=13).

Design: verification/codex-muse-role-alignment-design-20261108.md
Summary: verification/codex-muse-role-align-p1p2-20261108.md
Local only: not pushed, not merged, not deployed.

cloud/marker_tools.py

@@ -346,8 +346,15 @@ def extract_task_creates(text):
         executor = payload.get("executor")
         if executor is not None and executor not in EXECUTORS:
             continue
+        # 旁聊（P2 G7）：块里可显式指定 kind（"main"|"side"），
+        # 非法值整块跳过（与 executor 非法同款）；不指定时
+        # worker 按父任务 kind 继承（旁聊父 → 旁聊子）。
+        kind = payload.get("kind")
+        if kind is not None and kind not in ("main", "side"):
+            continue
         out.append({"name": name, "prompt": prompt, "model": model,
-                    "effort": effort, "executor": executor})
+                    "effort": effort, "executor": executor,
+                    "kind": kind})
     return out
 
 
@@ -1011,18 +1018,20 @@ def parent_spawn_generation(conn, parent_id):
 
     只数 parent_task_id 非空且 coordinator_part 为空的祖先链（即
     派生链）；协调员子任务（coordinator_part 非空）本身不是派生
-    任务，代数为 0，链到此为止。走 32 步仍未到头时按已数到的算，
-    绝不死循环。"""
+    任务，代数为 0，链到此为止；旁聊任务（kind='side'）同款——
+    旁聊不是 marker 派生，链到旁聊为止。走 32 步仍未到头时按已数
+    到的算，绝不死循环。"""
     generation = 0
     cur = parent_id
     for _ in range(32):
         if not cur:
             break
         row = conn.execute(
-            "SELECT parent_task_id, coordinator_part FROM tasks"
-            " WHERE id = ?", (cur,)).fetchone()
+            "SELECT * FROM tasks WHERE id = ?", (cur,)).fetchone()
         if row is None:
             break
+        if row_get(row, "kind") == "side":
+            break
         parent = row_get(row, "parent_task_id")
         part = row_get(row, "coordinator_part")
         if parent is not None and part is None:
@@ -1034,10 +1043,19 @@ def parent_spawn_generation(conn, parent_id):
 
 
 def count_direct_spawn_children(conn, parent_id):
-    """单个父任务的直接派生子任务数（不含协调员子任务）。"""
-    row = conn.execute(
-        "SELECT COUNT(*) FROM tasks WHERE parent_task_id = ?"
-        " AND coordinator_part IS NULL", (parent_id,)).fetchone()
+    """单个父任务的直接派生子任务数（不含协调员子任务与旁聊）。"""
+    try:
+        row = conn.execute(
+            "SELECT COUNT(*) FROM tasks WHERE parent_task_id = ?"
+            " AND coordinator_part IS NULL"
+            " AND (kind IS NULL OR kind != 'side')",
+            (parent_id,)).fetchone()
+    except Exception:
+        # 老库/最小测试表缺 kind 列：当时不可能有旁聊行，
+        # 不带 kind 条件的结果与带条件等价。
+        row = conn.execute(
+            "SELECT COUNT(*) FROM tasks WHERE parent_task_id = ?"
+            " AND coordinator_part IS NULL", (parent_id,)).fetchone()
     try:
         return int(row[0]) if row is not None else 0
     except (TypeError, ValueError, IndexError):