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>

integrations/common/__init__.py

@@ -1,3 +1,18 @@
 from .base import IntegrationConfig, IntegrationEvent, BaseIntegration, IntegrationManager
+from .secrets import SecretsManager, get_secrets, get_secret, require_secret
+from .redis_config import RedisConfig, get_redis_client, test_redis_connection, MockRedisClient
 
-__all__ = ['IntegrationConfig', 'IntegrationEvent', 'BaseIntegration', 'IntegrationManager']
+__all__ = [
+    'IntegrationConfig',
+    'IntegrationEvent',
+    'BaseIntegration',
+    'IntegrationManager',
+    'SecretsManager',
+    'get_secrets',
+    'get_secret',
+    'require_secret',
+    'RedisConfig',
+    'get_redis_client',
+    'test_redis_connection',
+    'MockRedisClient'
+]