feat(#71): implement graph data API

Implemented three new API endpoints for knowledge graph visualization:

1. GET /api/knowledge/graph - Full knowledge graph
   - Returns all entries and links with optional filtering
   - Supports filtering by tags, status, and node count limit
   - Includes orphan detection (entries with no links)

2. GET /api/knowledge/graph/stats - Graph statistics
   - Total entries and links counts
   - Orphan entries detection
   - Average links per entry
   - Top 10 most connected entries
   - Tag distribution across entries

3. GET /api/knowledge/graph/:slug - Entry-centered subgraph
   - Returns graph centered on specific entry
   - Supports depth parameter (1-5) for traversal distance
   - Includes all connected nodes up to specified depth

New Files:
- apps/api/src/knowledge/graph.controller.ts
- apps/api/src/knowledge/graph.controller.spec.ts

Modified Files:
- apps/api/src/knowledge/dto/graph-query.dto.ts (added GraphFilterDto)
- apps/api/src/knowledge/entities/graph.entity.ts (extended with new types)
- apps/api/src/knowledge/services/graph.service.ts (added new methods)
- apps/api/src/knowledge/services/graph.service.spec.ts (added tests)
- apps/api/src/knowledge/knowledge.module.ts (registered controller)
- apps/api/src/knowledge/dto/index.ts (exported new DTOs)
- docs/scratchpads/71-graph-data-api.md (implementation notes)

Test Coverage: 21 tests (all passing)
- 14 service tests including orphan detection, filtering, statistics
- 7 controller tests for all three endpoints

Follows TDD principles with tests written before implementation.
All code quality gates passed (lint, typecheck, tests).

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

docs/scratchpads/orch-110-git-ops.md

@@ -0,0 +1,102 @@
+# ORCH-110: Git Operations (clone, commit, push)
+
+## Objective
+
+Implement git operations service using simple-git library to support agent git workflows.
+
+## Acceptance Criteria
+
+- [x] `src/git/git-operations.service.ts` implemented
+- [x] Clone repository
+- [x] Create branch
+- [x] Commit changes with message
+- [x] Push to remote
+- [x] Git config (user.name, user.email from environment)
+- [x] NestJS service with proper dependency injection
+- [x] Comprehensive unit tests following TDD principles
+- [x] Mock simple-git for unit tests (no actual git operations)
+- [x] Test coverage >= 85%
+
+## Approach
+
+Following TDD (Red-Green-Refactor):
+
+1. **RED**: Write failing tests first
+   - Test git config setup
+   - Test clone repository
+   - Test create branch
+   - Test commit changes
+   - Test push to remote
+   - Test error handling
+
+2. **GREEN**: Implement minimum code to pass tests
+   - Create GitOperationsService with NestJS
+   - Implement each git operation
+   - Use simple-git library
+   - Read config from ConfigService
+
+3. **REFACTOR**: Improve code quality
+   - Extract common patterns
+   - Improve error messages
+   - Add type safety
+
+## Implementation Notes
+
+### Service Interface
+
+```typescript
+class GitOperationsService {
+  async cloneRepository(url: string, localPath: string): Promise<void>
+  async createBranch(localPath: string, branchName: string): Promise<void>
+  async commit(localPath: string, message: string): Promise<void>
+  async push(localPath: string, remote?: string, branch?: string): Promise<void>
+}
+```
+
+### Dependencies
+
+- simple-git: Git operations
+- @nestjs/config: Configuration
+- ConfigService: Access git config (userName, userEmail)
+
+### Testing Strategy
+
+- Mock simple-git using vitest.fn()
+- No actual git operations in tests
+- Test all success paths
+- Test error handling
+- Verify git config is set
+- Verify correct parameters passed to simple-git
+
+## Progress
+
+- [x] Create test file with failing tests
+- [x] Implement GitOperationsService
+- [x] All tests passing
+- [x] Coverage >= 85%
+- [x] Update git.module.ts
+- [x] Create types file
+- [x] Add index.ts exports
+
+## Testing Results
+
+```bash
+pnpm test src/git/git-operations.service.spec.ts --run
+# Test Files  1 passed (1)
+#      Tests  14 passed (14)
+
+pnpm test src/git/git-operations.service.spec.ts --coverage --run
+# Coverage: 100% statements, 85.71% branches, 100% functions, 100% lines
+# Exceeds 85% requirement ✓
+
+pnpm typecheck
+# No errors ✓
+```
+
+## Notes
+
+- simple-git already in package.json (v3.27.0)
+- Git config already in orchestrator.config.ts
+- Service uses dependency injection for testability
+- All git operations async
+- Error handling preserves original error messages