Add Phase 10-12 implementation: multi-tenant, marketplace, observability

Major additions:
- marketplace/: Agent template registry with FTS5 search, ratings, versioning
- observability/: Prometheus metrics, distributed tracing, structured logging
- ledger/migrations/: Database migration scripts for multi-tenant support
- tests/governance/: 15 new test files for phases 6-12 (295 total tests)
- bin/validate-phases: Full 12-phase validation script

New features:
- Multi-tenant support with tenant isolation and quota enforcement
- Agent marketplace with semantic versioning and search
- Observability with metrics, tracing, and log correlation
- Tier-1 agent bootstrap scripts

Updated components:
- ledger/api.py: Extended API for tenants, marketplace, observability
- ledger/schema.sql: Added tenant, project, marketplace tables
- testing/framework.ts: Enhanced test framework
- checkpoint/checkpoint.py: Improved checkpoint management

Archived:
- External integrations (Slack/GitHub/PagerDuty) moved to .archive/
- Old checkpoint files cleaned up

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

.archive/integrations/pagerduty/STATUS.md

@@ -0,0 +1,42 @@
+# Status: PagerDuty Integration
+
+## Current Phase
+
+**COMPLETE** (Module implemented, tests passing)
+
+## Summary
+
+PagerDuty integration module for incident management and alerting.
+
+## Tasks
+
+| Status | Task | Updated |
+|--------|------|---------|
+| ✓ | PagerDuty client implementation | 2026-01-23 |
+| ✓ | Events API v2 integration | 2026-01-23 |
+| ✓ | Unit tests (8/8 passing) | 2026-01-24 |
+
+## Files
+
+| File | Purpose |
+|------|---------|
+| `pagerduty.py` | Main PagerDuty integration class |
+| `__init__.py` | Module exports |
+
+## Dependencies
+
+- `common/base.py` (BaseIntegration)
+- `common/secrets.py` (SecretsManager)
+
+## Vault Path
+
+```
+secret/data/integrations/pagerduty
+```
+
+## Issues / Blockers
+
+None - awaiting production credentials at parent integration level.
+
+---
+*Last updated: 2026-01-24*