feat(fs): W4-E4 fsproxy hang isolation, partial sweep, replace-with-verify, TIMEOUT retry

- adapters/fs: FsProxy + fsworker run each file op in a killable subprocess;
  progress-stall watchdog (FS_HANG_TIMEOUT_MS) for copy/hash, total timeout for
  quick ops; SIGTERM -> SIGKILL -> FsError('TIMEOUT'); stat/checkRoot timeouts
  never read as missing
- copyWithVerify: onExisting conflict/skip/replace (hardlink backup + atomic
  rename, old file to .umt-trash or deleted), sweep stale partials before write,
  document why permissions/owner are not copied
- filesMatch/filesMatchSha256 throw FsError on read failure instead of
  match=false; crossDeviceMove skips redundant re-hash after sha256 copy
- FsErrorCode TIMEOUT + fsErrorClass; organize executeRecord routes fs ops
  through fsproxy, retries TIMEOUT/IO up to FS_TRANSFER_MAX_ATTEMPTS then opens
  a decision without deleting the record; reconcile errors no longer reported
  as EEXIST
- domain: subtitle .default marker (ORGANIZE_DEFAULT_SUBTITLE_LANG) and
  findOtherVersions (same season/episode/part, video only) as upgrade
  disposal candidates
- scripts/bench/fs-bench.ts and benchmark record in porting doc

Co-Authored-By: Claude Opus 5.5 <[email protected]>

packages/adapters/src/fs/fsworker.ts

@@ -0,0 +1,65 @@
+// fsproxy 执行子进程:从 stdin 读一条 JSON 请求,执行单个文件操作,stdout 逐行 JSON 上报
+// {t:"hb",phase,bytes,total}(按 progressIntervalMs 节流,阶段切换立即报)/ {t:"ok",result} / {t:"err",code,message}。
+// SIGTERM → 中止当前操作(copy 会清掉自己的 partial)后退出;挂死在系统调用里时由父进程 SIGKILL 回收。
+// 只依赖 node 内置模块,`deno run --no-config` 毫秒级启动。编译二进制可在入口按 --role fsworker 调 fsWorkerMain()。
+import { toFsError } from "./errors.ts";
+import { type FsOpRequest, type FsProgress, runFsOp } from "./fsops.ts";
+
+const enc = new TextEncoder();
+
+function send(obj: unknown): void {
+  try {
+    Deno.stdout.writeSync(enc.encode(`${JSON.stringify(obj)}\n`));
+  } catch {
+    // 父进程已退出:无处可报
+  }
+}
+
+/** 阻塞 JS 线程(测试用,模拟卡死的系统调用:信号监听器也不会运行) */
+function blockForever(): never {
+  const a = new Int32Array(new SharedArrayBuffer(4));
+  for (;;) Atomics.wait(a, 0, 0);
+}
+
+export async function fsWorkerMain(progressIntervalMs = Number(Deno.env.get("UMT_FS_PROGRESS_INTERVAL_MS") ?? 1000)) {
+  const req = JSON.parse(await new Response(Deno.stdin.readable).text()) as FsOpRequest;
+  const ac = new AbortController();
+  Deno.addSignalListener("SIGTERM", () => {
+    if (req._test?.ignoreTerm) return;
+    ac.abort();
+    // 操作卡在系统调用里时 abort 解不开:给清理一点时间后直接退出
+    setTimeout(() => Deno.exit(143), 500);
+  });
+  let lastAt = 0;
+  let lastPhase = "";
+  const progress = (p: FsProgress) => {
+    const hang = req._test?.hangAfterBytes;
+    const now = Date.now();
+    if (p.phase !== lastPhase || now - lastAt >= progressIntervalMs || (hang !== undefined && p.bytes >= hang)) {
+      lastAt = now;
+      lastPhase = p.phase;
+      send({ t: "hb", ...p });
+    }
+    if (hang !== undefined && p.bytes >= hang) blockForever();
+  };
+  if (req._test?.hangAfterBytes === 0) {
+    send({ t: "hb", phase: "start", bytes: 0, total: 0 });
+    blockForever();
+  }
+  try {
+    const result = await runFsOp(req, { signal: ac.signal, progress });
+    send({ t: "ok", result });
+  } catch (e) {
+    const fe = toFsError(e);
+    send({
+      t: "err",
+      code: ac.signal.aborted ? "ABORTED" : fe.code,
+      message: fe.message,
+      ...(fe.detail.path ? { path: fe.detail.path } : {}),
+      ...(fe.detail.syscall ? { syscall: fe.detail.syscall } : {}),
+    });
+  }
+  Deno.exit(0);
+}
+
+if (import.meta.main) await fsWorkerMain();