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/context.ts

@@ -21,6 +21,7 @@ export interface ConsoleCtx {
   models: string[]; modelCustomVisible: boolean;
   tasks: Task[]; taskCountText: string; taskError: string; refreshTasks: () => void;
   statusFilter: string; setStatusFilter: (v: string) => void; executorFilter: string; setExecutorFilter: (v: string) => void; searchText: string; setSearchText: (v: string) => void;
+  kindFilter: string; setKindFilter: (v: string) => void;
   filteredTasks: Task[];
   taskPage: number; taskTotalPages: number; taskTotal: number; taskStatusCounts: Record<string, number>; goToTaskPage: (p: number) => void;
   currentTask: Task | null; detailBody: string; actionMsg: string; actionReasons: string;
@@ -28,6 +29,8 @@ export interface ConsoleCtx {
   forkVisible: boolean; setForkVisible: (v: boolean) => void; forkTask: (msg: string) => Promise<void>; forkMsg: string;
   // Continue input is ContinuePanel (ChatInput); its send path is sendChatMessage below.
   coordChildren: Task[]; coordText: string; agents: Agent[]; agentsNote: string;
+  // 旁聊（Muse 角色对齐 P2）：当前任务的旁聊列表 + 派发器旁聊模式的父任务。
+  sideThreads: Task[]; sideParentId: string | null; setSideParentId: (v: string | null) => void;
   reviews: Review[]; reviewMsg: string; reviewError: string; refreshReviews: () => void; postReview: (body: ReviewBody) => Promise<void>; submitFindings: (id: string) => void;
   traceEntries: TraceEntry[]; traceNote: string; traceDone: string; traceKind: string; setTraceKind: (v: string) => void; downloadTrace: () => void; traceMsg: string;
   sendChatMessage: (text: string) => Promise<void>; chatMsg: string;