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>

marketplace/templates/README.md

@@ -0,0 +1,69 @@
+# Marketplace Templates Storage
+
+> Local file storage for agent template content
+
+## Overview
+
+This directory stores the actual template content files for the agent marketplace. Template metadata is stored in SQLite, while the template definitions (YAML/JSON configurations) are stored here.
+
+## Directory Structure
+
+```
+templates/
+├── {template_id}/
+│   ├── {version}/
+│   │   ├── template.yaml    # Agent configuration template
+│   │   ├── schema.json      # JSON Schema for config validation
+│   │   └── assets/          # Additional template assets
+│   └── latest -> v1.0.0/    # Symlink to latest stable
+└── README.md
+```
+
+## Template Format
+
+Templates are YAML files defining agent configurations:
+
+```yaml
+# template.yaml
+name: "My Agent Template"
+version: "1.0.0"
+tier: 0
+
+config:
+  capabilities:
+    - read_files
+    - execute_commands
+
+  constraints:
+    max_execution_time: 300
+    allowed_paths:
+      - /opt/workspace
+
+  tools:
+    - name: bash
+      allowed_commands:
+        - git
+        - npm
+
+variables:
+  - name: workspace_path
+    type: string
+    required: true
+    description: "Path to the project workspace"
+```
+
+## Usage
+
+Templates are managed through the Marketplace API:
+- Publishing creates entries here
+- Versions are stored in subdirectories
+- Content is hashed for integrity verification
+
+## Status
+
+**Complete**
+
+See [STATUS.md](./STATUS.md) for detailed progress tracking.
+
+---
+*Last updated: 2026-01-24 UTC*

marketplace/templates/STATUS.md

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+# Status: Marketplace Templates Storage
+
+## Current Phase
+
+**COMPLETE**
+
+## Tasks
+
+| Status | Task | Updated |
+|--------|------|---------|
+| ✅ | Directory structure defined | 2026-01-24 |
+| ✅ | Template format documented | 2026-01-24 |
+| ✅ | Integration with Marketplace API | 2026-01-24 |
+
+## Notes
+
+This is a storage directory for template files. Templates are created dynamically when published through the Marketplace API.
+
+## Dependencies
+
+- Marketplace API (`/opt/agent-governance/marketplace/api.py`)
+
+## Issues / Blockers
+
+*No current issues or blockers.*
+
+## Activity Log
+
+### 2026-01-24 UTC
+- **Phase**: COMPLETE
+- **Action**: Documentation added
+- **Details**: Created README.md and STATUS.md
+
+---
+*Last updated: 2026-01-24 UTC*