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>

ledger/migrations/README.md

@@ -0,0 +1,84 @@
+# Ledger Migrations
+
+> SQL schema migrations for the governance ledger database
+
+## Overview
+
+This directory contains SQL migration files that define and evolve the SQLite database schema for the agent governance system. Migrations are numbered sequentially and should be applied in order.
+
+## Migration Files
+
+| File | Phase | Description |
+|------|-------|-------------|
+| `001_multi_tenant.sql` | Phase 10 | Multi-tenant support tables |
+| `002_marketplace.sql` | Phase 11 | Agent marketplace tables |
+
+## Migration 001: Multi-Tenant Support
+
+Adds tables for multi-tenant architecture:
+
+| Table | Purpose |
+|-------|---------|
+| `tenants` | Organization/customer records |
+| `projects` | Workspaces within tenants |
+| `tenant_quotas` | Resource limits per tenant |
+| `tenant_usage` | Usage tracking for billing |
+| `api_keys` | API authentication keys |
+| `user_roles` | RBAC role assignments |
+| `audit_log_tenant` | Tenant-scoped audit trail |
+
+## Migration 002: Marketplace
+
+Adds tables for the agent template marketplace:
+
+| Table | Purpose |
+|-------|---------|
+| `agent_templates` | Core template registry |
+| `template_versions` | Version history with semver |
+| `template_installations` | Installation tracking |
+| `template_ratings` | User ratings and reviews |
+| `template_downloads` | Download metrics |
+| `templates_fts` | FTS5 full-text search index |
+
+## Applying Migrations
+
+Migrations are applied automatically when the ledger API starts, or can be applied manually:
+
+```bash
+# Apply all migrations
+sqlite3 /opt/agent-governance/ledger/governance.db < 001_multi_tenant.sql
+sqlite3 /opt/agent-governance/ledger/governance.db < 002_marketplace.sql
+
+# Verify tables
+sqlite3 /opt/agent-governance/ledger/governance.db ".tables"
+```
+
+## Schema Conventions
+
+- Primary keys: `{entity}_id TEXT PRIMARY KEY`
+- Timestamps: `TEXT DEFAULT CURRENT_TIMESTAMP` (ISO 8601)
+- Foreign keys: `REFERENCES {table}({column}) ON DELETE CASCADE`
+- JSON storage: `TEXT` columns with JSON content
+- Boolean: `INTEGER` (0/1)
+- Indices: Created for frequently queried columns
+
+## Adding New Migrations
+
+1. Create file: `00N_description.sql`
+2. Use `CREATE TABLE IF NOT EXISTS` for idempotency
+3. Add indices for query performance
+4. Document in this README
+5. Test with fresh database
+
+## Status
+
+**Complete**
+
+See [STATUS.md](./STATUS.md) for detailed progress tracking.
+
+## Architecture Reference
+
+Part of the [Ledger System](/opt/agent-governance/ledger/README.md).
+
+---
+*Last updated: 2026-01-24 UTC*