fix(mitm): recover from stale lock file on server start

Detect dead PID in lock file and reclaim it instead of failing, and drop unused fs dependency.

Co-authored-by: Cursor <cursoragent@cursor.com>

package.json

@@ -24,7 +24,6 @@
     "bcryptjs": "^3.0.3",
     "confbox": "^0.2.4",
     "express": "^5.2.1",
-    "fs": "^0.0.1-security",
     "http-proxy-middleware": "^3.0.5",
     "jose": "^6.1.3",
     "marked": "^18.0.1",

src/mitm/manager.js

@@ -496,9 +496,15 @@ async function startServer(apiKey, sudoPassword, forceKillPort443 = false) {
     fs.writeFileSync(LOCK_FILE, String(process.pid), { flag: "wx" });
   } catch (e) {
     if (e.code === "EEXIST") {
-      throw new Error("MITM server is already starting (lock contention)");
-    }
-    throw e;
+      let stale = false;
+      try {
+        const pid = parseInt(fs.readFileSync(LOCK_FILE, "utf-8").trim(), 10);
+        stale = !pid || !isProcessAlive(pid);
+      } catch { stale = true; } // unreadable lock → treat as stale
+      if (!stale) throw new Error("MITM server is already starting (lock contention)");
+      try { fs.unlinkSync(LOCK_FILE); } catch { /* ignore */ }
+      fs.writeFileSync(LOCK_FILE, String(process.pid), { flag: "wx" });
+    } else throw e;
   }
 
   try {