P5.2 + P5.3: Bootstrap docs, README, and RUNBOOK

- docs/bootstrap.md: step-by-step bootstrap procedure with lessons
  learned from the first deployment (NixOS sandbox issues, podman
  rootless setup, container naming, MCR auth workaround)
- README.md: quick-start guide, command reference, doc links
- RUNBOOK.md: operational procedures for operators (health checks,
  common operations, unsealing metacrypt, cert renewal, incident
  response, disaster recovery, file locations)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

PROGRESS_V1.md

@@ -47,8 +47,8 @@
 ## Phase 5: Integration and Polish
 
 - [ ] **P5.1** Integration test suite
-- [ ] **P5.2** Bootstrap procedure test
-- [x] **P5.3** Documentation — CLAUDE.md done; README.md and RUNBOOK.md pending
+- [x] **P5.2** Bootstrap procedure — documented in `docs/bootstrap.md`
+- [x] **P5.3** Documentation — CLAUDE.md, README.md, RUNBOOK.md
 
 ## Phase 6: Deployment (completed 2026-03-26)