test(A1.9): Add comprehensive E2E tests for git source features

Added 16 new E2E tests covering complete workflows:

Core Git Operations (12 tests):
- test_e2e_workflow_direct_git_url - Clone and fetch without registration
- test_e2e_workflow_with_source_registration - Complete CRUD workflow
- test_e2e_multiple_sources_priority_resolution - Multi-source management
- test_e2e_pull_existing_repository - Pull updates from upstream
- test_e2e_force_refresh - Delete and re-clone cache
- test_e2e_config_not_found - Error handling with helpful messages
- test_e2e_invalid_git_url - URL validation
- test_e2e_source_name_validation - Name validation
- test_e2e_registry_persistence - Cross-instance persistence
- test_e2e_cache_isolation - Independent cache directories
- test_e2e_auto_detect_token_env - Auto-detect GITHUB_TOKEN, GITLAB_TOKEN
- test_e2e_complete_user_workflow - Real-world team collaboration scenario

MCP Tools Integration (4 tests):
- test_mcp_add_list_remove_source_e2e - All 3 source management tools
- test_mcp_fetch_config_git_url_mode_e2e - fetch_config with direct git URL
- test_mcp_fetch_config_source_mode_e2e - fetch_config with registered source
- test_mcp_error_handling_e2e - Error cases for all 4 tools

Test Features:
- Uses temporary directories and actual git repositories
- Tests with file:// URLs (no network required)
- Validates all error messages
- Tests registry persistence across instances
- Tests cache isolation
- Simulates team collaboration workflows

All tests use real GitPython operations and validate:
- Clone/pull with shallow clones
- Config discovery and fetching
- Source registry CRUD
- Priority resolution
- Token auto-detection
- Error handling with helpful messages

Fixed test_mcp_git_sources.py import error (moved TextContent import inside try/except)

Test Results: 522 passed, 62 skipped (95 new tests added for A1.9)

🤖 Generated with Claude Code
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

tests/test_mcp_git_sources.py

@@ -9,14 +9,15 @@ import pytest
 import os
 from pathlib import Path
 from unittest.mock import AsyncMock, MagicMock, patch, Mock
-from mcp.types import TextContent
 
 # Test if MCP is available
 try:
     import mcp
+    from mcp.types import TextContent
     MCP_AVAILABLE = True
 except ImportError:
     MCP_AVAILABLE = False
+    TextContent = None  # Define placeholder
 
 
 @pytest.fixture