fix: robustness improvements — atomic writes, timeouts, shell injection, validation errors

- Atomic JSON writes (write-to-tmp + rename) prevent queue/log corruption
- Per-job (3min) and overall run (45min) timeouts prevent hangs
- execFileSync in ai_answer.mjs prevents shell injection with resume paths
- Validation error detection after form fill in Easy Apply modal
- Config-driven enabled_apply_types (from settings.json)
- isRequired() detects required/aria-required/label * patterns
- getLabel() strips trailing * from required field labels
- Actionable logging on failures ("Action: ..." messages)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/queue.mjs

@@ -3,7 +3,7 @@
  * Handles jobs_queue.json read/write/update
  * Uses in-memory cache to avoid redundant disk I/O within a run.
  */
-import { readFileSync, writeFileSync, existsSync, mkdirSync } from 'fs';
+import { readFileSync, writeFileSync, renameSync, existsSync, mkdirSync } from 'fs';
 import { dirname, resolve } from 'path';
 import { fileURLToPath } from 'url';
 
@@ -37,6 +37,17 @@ function ensureDir(path) {
   if (!existsSync(dir)) mkdirSync(dir, { recursive: true });
 }
 
+/**
+ * Atomic write — writes to a temp file then renames.
+ * Prevents corruption if two processes write simultaneously or the process
+ * crashes mid-write. rename() is atomic on POSIX filesystems.
+ */
+function atomicWriteJSON(filePath, data) {
+  const tmp = filePath + '.tmp';
+  writeFileSync(tmp, JSON.stringify(data, null, 2));
+  renameSync(tmp, filePath);
+}
+
 // --- In-memory caches (populated on first read, invalidated on write) ---
 let _queueCache = null;
 let _logCache = null;
@@ -50,7 +61,7 @@ export function loadQueue() {
 
 export function saveQueue(jobs) {
   ensureDir(QUEUE_PATH);
-  writeFileSync(QUEUE_PATH, JSON.stringify(jobs, null, 2));
+  atomicWriteJSON(QUEUE_PATH, jobs);
   _queueCache = jobs;
 }
 
@@ -62,7 +73,8 @@ function loadLog() {
 }
 
 function saveLog(log) {
-  writeFileSync(LOG_PATH, JSON.stringify(log, null, 2));
+  ensureDir(LOG_PATH);
+  atomicWriteJSON(LOG_PATH, log);
   _logCache = log;
 }