v0.2.0: Separate enrichment worker, fast remember()

Major changes:
- remember() now completes in ~40ms (was 28+ seconds)
- Enrichment (embedding, dedup) runs in separate worker process
- New systemd service: opencode-memory-enrich
- Boot context shows available updates from git
- Added reminder and procedure review features

New tools:
- set_reminder, clear_reminder, advance_reminder
- mark_procedure_reviewed, set_review_interval

Breaking: Requires running both services (setup.sh handles this automatically)