chore(deps): refresh locks and harden engine promotion

- refresh compatible npm and Cargo lockfile dependencies
- update locked Windows and Linux FFmpeg provider artifacts by checksum
- publish verified engine payloads with interrupted-promotion recovery
- retry Windows-safe cleanup and cover worst-case promotion states

scripts/engine-payload-promotion.js

@@ -0,0 +1,137 @@
+import fs from 'node:fs';
+import path from 'node:path';
+
+const RETRY_DELAYS_MS = [100, 250, 500, 1_000, 2_000];
+
+function pathExists(value) {
+  try {
+    fs.lstatSync(value);
+    return true;
+  } catch (error) {
+    if (error?.code === 'ENOENT') return false;
+    throw error;
+  }
+}
+
+function previousPayloadPrefix(destination) {
+  return `.${path.basename(destination)}.previous-`;
+}
+
+function previousPayloads(destination) {
+  const parent = path.dirname(destination);
+  const prefix = previousPayloadPrefix(destination);
+  return fs.readdirSync(parent, { withFileTypes: true })
+    .filter(entry => entry.name.startsWith(prefix))
+    .map(entry => path.join(parent, entry.name));
+}
+
+function previousPayloadOwner(destination, candidate) {
+  const suffix = path.basename(candidate).slice(previousPayloadPrefix(destination).length);
+  const separator = suffix.indexOf('-');
+  const pid = separator >= 0 ? suffix.slice(0, separator) : suffix;
+  return /^\d+$/.test(pid) ? Number(pid) : null;
+}
+
+function isProcessAlive(pid) {
+  if (!Number.isSafeInteger(pid) || pid <= 0) return false;
+  try {
+    process.kill(pid, 0);
+    return true;
+  } catch (error) {
+    return error?.code === 'EPERM';
+  }
+}
+
+async function removeOrphanedPreviousPayloads(destination) {
+  for (const candidate of previousPayloads(destination)) {
+    const owner = previousPayloadOwner(destination, candidate);
+    if (owner === null || isProcessAlive(owner)) continue;
+    await removePathWithRetry(candidate);
+  }
+}
+
+/**
+ * Restores the only previous payload left by a process that died after moving
+ * the destination aside but before publishing its replacement. Multiple
+ * candidates are ambiguous and remain untouched for manual recovery.
+ */
+export function recoverInterruptedPromotion(destination) {
+  if (pathExists(destination)) return;
+
+  const candidates = previousPayloads(destination);
+  if (candidates.length === 0) return;
+  if (candidates.length > 1) {
+    throw new Error(
+      `Cannot recover engine payload at ${destination}: found ${candidates.length} previous payloads`
+    );
+  }
+
+  const candidate = candidates[0];
+  if (!fs.lstatSync(candidate).isDirectory()) {
+    throw new Error(`Cannot recover engine payload from non-directory backup: ${candidate}`);
+  }
+  fs.renameSync(candidate, destination);
+}
+
+function sleep(milliseconds) {
+  return new Promise(resolve => setTimeout(resolve, milliseconds));
+}
+
+export async function removePathWithRetry(value) {
+  for (let attempt = 0; ; attempt += 1) {
+    try {
+      fs.rmSync(value, { recursive: true, force: true });
+      return;
+    } catch (error) {
+      const retryable = process.platform === 'win32'
+        && ['EACCES', 'EBUSY', 'EPERM'].includes(error?.code);
+      if (!retryable || attempt >= RETRY_DELAYS_MS.length) throw error;
+      await sleep(RETRY_DELAYS_MS[attempt]);
+    }
+  }
+}
+
+/**
+ * Publishes a fully verified payload without exposing a partially written
+ * directory. The staging directory must share a filesystem with destination.
+ */
+export async function promoteDirectory(staging, destination) {
+  recoverInterruptedPromotion(destination);
+  const stagingStats = fs.lstatSync(staging);
+  if (!stagingStats.isDirectory()) {
+    throw new Error(`Engine payload staging path is not a directory: ${staging}`);
+  }
+
+  const parent = path.dirname(destination);
+  const backup = path.join(
+    parent,
+    `.${path.basename(destination)}.previous-${process.pid}-${process.hrtime.bigint()}`
+  );
+  let movedExisting = false;
+
+  try {
+    if (pathExists(destination)) {
+      fs.renameSync(destination, backup);
+      movedExisting = true;
+    }
+    fs.renameSync(staging, destination);
+  } catch (error) {
+    if (movedExisting && !pathExists(destination) && pathExists(backup)) {
+      try {
+        fs.renameSync(backup, destination);
+      } catch (restoreError) {
+        throw new AggregateError(
+          [error, restoreError],
+          `Failed to publish engine payload and restore the previous payload at ${destination}`
+        );
+      }
+    } else if (movedExisting && pathExists(destination) && pathExists(backup)) {
+      // Another provisioner won the promotion race; discard only our backup.
+      await removePathWithRetry(backup);
+    }
+    throw error;
+  }
+
+  if (movedExisting) await removePathWithRetry(backup);
+  await removeOrphanedPreviousPayloads(destination);
+}