feat: Integrate Requirements Engineering Agent and fix Issue #59 test failures

## Major Integration

- ✅ Integrated Requirements Engineering Agent into development workflow
- ✅ Enhanced Makefile with requirements validation targets
- ✅ Added pre-commit validation with mock compatibility checking
- ✅ Enhanced TDD workflow to include foundation analysis

## Test Fixes

- ✅ Fixed GiteaPlugin missing _add_comment_async method
- ✅ Fixed LocalPlugin config.yml file not found errors in tests
- ✅ Enhanced mock objects in CLI tests with proper domain model attributes
- ✅ All Issue #59 tests now passing (38/38 tests pass)

## New Capabilities

- `make validate-requirements` - Foundation analysis before development
- `make check-interface-compatibility INTERFACE=Name` - Interface compatibility checking
- `make generate-dev-checklist FEATURE='Name'` - Development checklist generation
- `make validate-mocks` - Mock object compatibility validation
- `make pre-commit-validate` - Complete pre-commit validation workflow

## Problem Prevention

This integration prevents the exact interface compatibility issues and mock object
mismatches that caused hours of debugging in Issue #59. The Requirements Engineering
Agent provides proactive foundation analysis and catches problems before they occur.

🤖 Generated with Claude Code

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

tests/test_issue_59_plugin_manager.py

@@ -162,13 +162,12 @@ class TestPluginConfiguration:
         }
 
         with patch.object(IssuePluginManager, '_load_config', return_value=config):
-            manager = IssuePluginManager()
-
-            # Mock the plugin class to verify config is passed
-            with patch.object(manager.plugins, 'get') as mock_get:
+            with patch.object(IssuePluginManager, '_discover_plugins') as mock_discover:
+                # Mock the plugin class to verify config is passed
                 mock_plugin_class = Mock()
-                mock_get.return_value = mock_plugin_class
+                mock_discover.return_value = {'gitea': mock_plugin_class}
 
+                manager = IssuePluginManager()
                 manager.get_backend('gitea')
 
                 # Verify plugin was initialized with backend config
@@ -182,12 +181,11 @@ class TestPluginConfiguration:
         }
 
         with patch.object(IssuePluginManager, '_load_config', return_value=config):
-            manager = IssuePluginManager()
-
-            with patch.object(manager.plugins, 'get') as mock_get:
+            with patch.object(IssuePluginManager, '_discover_plugins') as mock_discover:
                 mock_plugin_class = Mock()
-                mock_get.return_value = mock_plugin_class
+                mock_discover.return_value = {'local': mock_plugin_class}
 
+                manager = IssuePluginManager()
                 manager.get_backend('local')
 
                 # Should initialize with empty config