fix(cli): close the Remote Control lock write race and tighten artifact modes

- an unreadable lock is a rival mid-write, not a stale one: `open(…, 'wx')`
  publishes an empty file before its JSON lands, so removing it let both
  processes believe they held the lock. Re-read before sweeping, and sweep
  only once it is still unreadable at the end
- chmod the QR directory and image, since mode only applies to paths the
  call creates
- resolve the relay origin inside the try, so a malformed setting reports
  through the startup handler

Author: elkaix

apps/pythinker-code/src/cli/sub/web/remote-control-lock.ts

@@ -1,4 +1,5 @@
 import { randomBytes } from 'node:crypto';
+import { setTimeout as sleep } from 'node:timers/promises';
 import { mkdir, open, readFile, unlink } from 'node:fs/promises';
 import { dirname, join } from 'node:path';
 
@@ -47,6 +48,7 @@ export interface RemoteControlLock {
 }
 
 const MAX_ACQUIRE_ATTEMPTS = 3;
+const ACQUIRE_RETRY_DELAY_MS = 25;
 
 export async function acquireRemoteControlLock(
   homeDir: string,
@@ -83,6 +85,15 @@ export async function acquireRemoteControlLock(
       if (holder !== undefined && pidAlive(holder.pid)) {
         throw new RemoteControlAlreadyRunningError(holder);
       }
+      // `open(…, 'wx')` publishes an empty file before its JSON is written, so
+      // an unreadable lock may simply be a rival mid-write. Deleting it there
+      // would let both processes believe they hold the lock. Give the writer a
+      // moment and re-read; only sweep it once it is still unreadable at the
+      // end, which is the genuinely corrupt case.
+      if (holder === undefined && attempt < MAX_ACQUIRE_ATTEMPTS) {
+        await sleep(ACQUIRE_RETRY_DELAY_MS);
+        continue;
+      }
       if (attempt >= MAX_ACQUIRE_ATTEMPTS) {
         throw new Error(
           `Unable to acquire the Remote Control lock at ${lockPath}. Another process keeps recreating it.`, { cause: error },

apps/pythinker-code/src/tui/commands/web.ts

@@ -62,9 +62,11 @@ export async function handleRemoteControlCommand(host: SlashCommandHost): Promis
 
   host.setExitForegroundTask(async () => {
     const options = parseServerOptions({});
-    const relayOrigin = resolveRelayOrigin();
     let remoteControl: Awaited<ReturnType<typeof startRemoteControl>> | undefined;
     try {
+      // Inside the try: a malformed relay setting throws here, and the user
+      // should see it through the same handler as any other startup failure.
+      const relayOrigin = resolveRelayOrigin();
       await startServerForeground(options, {
         onReady: async (origin) => {
           const dataDir = getDataDir();

apps/pythinker-code/src/utils/remote-control-qr.ts

@@ -1,4 +1,4 @@
-import { mkdir, writeFile } from 'node:fs/promises';
+import { chmod, mkdir, writeFile } from 'node:fs/promises';
 import { resolve } from 'node:path';
 
 import {
@@ -22,9 +22,13 @@ export async function generateRemoteControlQr(
   dataDir: string,
 ): Promise<{ terminal: string; pngPath: string }> {
   await mkdir(dataDir, { recursive: true, mode: 0o700 });
+  // `mode` only applies to paths these calls create; tighten an existing dir
+  // or an earlier run's image too.
+  await chmod(dataDir, 0o700);
   const pngPath = resolve(dataDir, 'rc-qrcode.png');
   const png = await QRCode.toBuffer(url, { type: 'png', margin: QR_PNG_MARGIN });
   await writeFile(pngPath, png, { mode: 0o600 });
+  await chmod(pngPath, 0o600);
   const terminal = renderInlineImageQr(url, png) ?? renderTerminalQr(url);
   return { terminal, pngPath };
 }

apps/pythinker-code/test/cli/web/remote-control.test.ts

@@ -146,7 +146,7 @@ describe('Remote Control HTTP forwarding', () => {
     ).toString();
     expect(html).not.toContain('</script><script>alert(1)');
     expect(html).toContain('\\u003c/script\\u003e');
-    expect(html.match(/<script>/g)).toHaveLength(1);
+    expect(html.split('<script>')).toHaveLength(2);
   });
 
   it('rejects absolute-form and malformed request targets', () => {