Replace Reclaim.ai?

Build me a personal calendar auto-blocker to replace Reclaim.ai, for one Google
Calendar, mine. Requirements:

- A Node script on a 30-minute cron (node-cron or plain crontab): googleapis for
  Calendar, better-sqlite3 for state, config in a YAML file. No web UI.
- config.yaml defines habits and tasks: name, duration, ideal window (e.g. gym, 60 min,
  weekdays 16:00-19:00), times per week, and priority.
- Each run: read free/busy for the next 7 days and place holds for unscheduled habits
  inside their windows, highest priority first.
- Tag every event it creates with a marker string in the description; the script may
  only ever move or delete events carrying that marker.
- If a meeting lands on a hold, re-place the hold at the next free slot in its window
  and append the move to a plain-text log.
- `blocker plan` prints next week's placements as a table before anything is written;
  `blocker clear` removes every machine-created hold.
- OAuth client credentials and refresh token in .env; budget an hour for the Google
  Cloud console, it is genuinely annoying.
- Out of scope: scheduling links, team coordination, and multi-calendar juggling. Never
  touch or decline events it did not create.
- README: Google Cloud console steps, the calendar scopes needed, and the first-run auth
  flow.