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/console-react/src/sections/detail/DetailActions.tsx

@@ -12,18 +12,23 @@ export default function DetailActions() {
   if (!t) return null;
   const terminal = TRACE_TERMINAL.includes(t.status);
   const retryOk = ["failed", "interrupted", "merge-failed"].includes(t.status);
+  // 旁聊（Muse 角色对齐 P2）：无 worktree/分支，后端 /fork /merge
+  // /pr 一律 409，这里只留重试/取消/查成本，不渲染那三处入口。
+  const isSide = t.kind === "side";
   return (
     <>
       <Bar>
         <button disabled={!retryOk} title={retryOk ? "" : "仅 failed/interrupted/merge-failed 可重试"} onClick={() => ctx.doAction("retry")}>重试</button>
         <button className="danger" disabled={terminal} title={terminal ? "终态任务不可取消" : ""} onClick={() => ctx.doAction("cancel")}>取消</button>
-        <button disabled={t.status !== "completed"} title={t.status !== "completed" ? "仅 completed 可合并" : ""} onClick={() => ctx.doAction("merge")}>合并（completed → merged）</button>
-        <button disabled={t.status !== "merged"} title={t.status !== "merged" ? "仅 merged 可提 PR" : ""} onClick={() => ctx.doAction("pr")}>提 PR（须 merged）</button>
-        {terminal ? <button onClick={() => ctx.setForkVisible(true)}>分支</button> : null}
+        {isSide ? null : (<>
+          <button disabled={t.status !== "completed"} title={t.status !== "completed" ? "仅 completed 可合并" : ""} onClick={() => ctx.doAction("merge")}>合并（completed → merged）</button>
+          <button disabled={t.status !== "merged"} title={t.status !== "merged" ? "仅 merged 可提 PR" : ""} onClick={() => ctx.doAction("pr")}>提 PR（须 merged）</button>
+        </>)}
+        {terminal && !isSide ? <button onClick={() => ctx.setForkVisible(true)}>分支</button> : null}
         <button onClick={ctx.taskCost}>查成本</button>
         <span className="muted">{ctx.actionMsg} {ctx.actionReasons}</span>
       </Bar>
-      {ctx.forkVisible ? (
+      {ctx.forkVisible && !isSide ? (
         <div>
           <input type="text" placeholder="分支首轮消息（必填，带历史的新会话）" style={{ width: "100%", boxSizing: "border-box", margin: "6px 0" }} value={forkMsg} onChange={(e) => setForkMsg(e.target.value)} />
           <Bar><button className="seal" onClick={async () => { await ctx.forkTask(forkMsg); setForkMsg(""); }}>创建分支任务</button><span className="muted">{ctx.forkMsg}</span></Bar>

cloud/console-react/src/sections/detail/DetailLists.tsx

@@ -19,6 +19,23 @@ export function CoordPanel() {
   );
 }
 
+// 旁聊（Muse 角色对齐 P2）：当前任务挂着的旁聊线程，与协调员
+// 子任务列表同款组件复用；点行切到该旁聊的详情。
+export function SideThreadPanel() {
+  const ctx = useConsole();
+  if (!ctx.currentTask) return <div className="muted">点任务行查看详情后，这里显示旁聊</div>;
+  if (ctx.sideThreads.length === 0) return <div className="muted">（暂无旁聊；列表“开旁聊”可在此任务下新建，不建 worktree）</div>;
+  return (
+    <DataListRaw>
+      {ctx.sideThreads.map((k) => (
+        <li key={k.id} onClick={() => ctx.showDetail(k.id)} style={{ cursor: "pointer" }}>
+          <span className="row-main">旁聊 ｜ 状态 <span className={"st-" + k.status}>{k.status}</span> ｜ {shortId(k.id)} ｜ {String(k.prompt || "").slice(0, 60)}</span>
+        </li>
+      ))}
+    </DataListRaw>
+  );
+}
+
 export function AgentsPanel() {
   const ctx = useConsole();
   if (!ctx.currentTask) return <div className="muted">点任务行查看详情后，这里显示子代理链路</div>;