feat(whatsapp): simplify API with session URL deeplinks

- Add simplified notification API: notify(), notifyChoice(), notifyStep()
- Add automatic session URL deeplinks (https://claude.ai/code/session_xxx)
- Reduce default commands to essentials: help, status, sessions, remote
- Consolidate tests from 606 to 499 (remove stubs, merge duplicates)
- Remove complex commands (approve, merge, build, test, lint, git ops)

New simplified API:
  notify(message) - simple status
  notifyChoice(msg, optA, optB) - A/B choice (1 or 2)
  notifyStep(step, status) - step completion
  getSessionUrl() - get Claude session deeplink

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: jonathanpeterwu