refactor: normalize apply statuses, remove dead code, fix signal handler

- lib/apply/index.mjs: add STATUS_MAP to normalize platform-specific statuses
  to generic ones (no_button/no_submit/no_modal → skipped_no_apply).
  Documented all generic statuses for AI/developer reference.
- job_applier.mjs: handleResult now handles skipped_no_apply, default case
  logs + saves instead of silently dropping
- lib/linkedin.mjs: remove dead applyLinkedIn() and detectAts(), clean imports
  (~110 lines removed). Search-only module now.
- lib/wellfound.mjs: remove dead applyWellfound(), clean imports.
  Search-only module now.
- lib/lock.mjs: fix async signal handler — shutdown handlers now actually
  complete before process.exit()
- test_linkedin_login.mjs: add try/catch/finally with proper browser cleanup
- README: update status table with all current statuses

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

lib/apply/index.mjs

@@ -44,9 +44,32 @@ export function supportedTypes() {
   return Object.keys(REGISTRY);
 }
 
+/**
+ * Status normalization — handlers return platform-specific statuses,
+ * this map converts them to generic statuses that job_applier.mjs understands.
+ *
+ * Generic statuses (what handleResult expects):
+ *   submitted                   — application was submitted successfully
+ *   needs_answer                — blocked on unknown form question, sent to Telegram
+ *   skipped_recruiter_only      — LinkedIn recruiter-only listing
+ *   skipped_external_unsupported — external ATS not yet implemented
+ *   skipped_no_apply            — no apply button/modal/submit found on page
+ *   skipped_honeypot            — honeypot question detected, application abandoned
+ *   stuck                       — modal progress stalled after retries
+ *   incomplete                  — ran out of modal steps without submitting
+ *
+ * When adding a new handler, return any status you want — if it doesn't match
+ * a generic status above, add a mapping here so job_applier doesn't need to change.
+ */
+const STATUS_MAP = {
+  no_button:  'skipped_no_apply',
+  no_submit:  'skipped_no_apply',
+  no_modal:   'skipped_no_apply',
+};
+
 /**
  * Apply to a job using the appropriate handler
- * Returns result object with status
+ * Returns result object with normalized status
  */
 export async function applyToJob(page, job, formFiller) {
   const handler = getHandler(job.apply_type);
@@ -58,5 +81,6 @@ export async function applyToJob(page, job, formFiller) {
       ats_platform: job.apply_type || 'unknown',
     };
   }
-  return handler.apply(page, job, formFiller);
+  const result = await handler.apply(page, job, formFiller);
+  return { ...result, status: STATUS_MAP[result.status] || result.status };
 }