Achieve 100% test coverage with comprehensive improvements

Enhanced test suite from 97% to 100% coverage with 173 passing tests.

## New Features

### 1. Error Handling Tests (3 tests)
- test_add_message_handles_read_error_gracefully
- test_add_message_handles_write_error_gracefully
- test_clear_user_history_handles_permission_error
- test_logger_reuses_existing_handlers

Coverage: memory.py 91% → 100%, utils.py 98% → 100%

### 2. Integration Tests (9 tests) - test_integration.py
- test_mention_to_response_workflow: Full message flow
- test_conversation_context_preserved: Multi-turn conversations
- test_config_to_components_integration: Component initialization
- test_error_recovery_workflow: Graceful error handling
- test_mention_detection_integration_with_nicknames
- test_memory_limit_enforcement_in_workflow
- test_ambiguous_greeting_workflow
- test_logger_integration_with_memory
- test_logger_integration_with_ai_provider
- test_config_validation_workflow

### 3. Parameterized Tests (45 tests)
- 18 mention detection test cases
- 17 greeting detection test cases
- 8 content extraction test cases
- Covers edge cases, unicode, nicknames, false positives

### 4. GitHub Actions CI Workflow
- Multi-Python version testing (3.9, 3.10, 3.11, 3.12)
- Automated coverage reporting
- Code quality checks (Black, isort, flake8)
- Codecov integration
- Coverage badge generation

## Test Statistics

- Tests: 116 → 173 (+49% increase)
- Coverage: 97% → 100% (+3pp)
- Execution time: ~1.1 seconds
- All components: 100% coverage

## Files Modified

- tests/test_utils.py: Added parameterized tests and error handling
- tests/test_memory.py: Added error handling tests
- tests/test_integration.py: NEW - Full integration test suite
- tests/README.md: Updated documentation
- .github/workflows/test.yml: NEW - CI/CD automation

tests/test_memory.py

@@ -327,3 +327,39 @@ class TestConversationMemory:
         # Only message within retention should be kept
         assert len(retrieved) == 1
         assert retrieved[0]["content"] == "Just under boundary"
+
+    def test_add_message_handles_read_error_gracefully(self, temp_dir, mocker):
+        """Test that add_message handles file read errors gracefully"""
+        memory = ConversationMemory(data_dir=str(temp_dir))
+
+        # Create a file first
+        memory.add_message("testuser", "user", "First message")
+
+        # Mock json.load to raise an exception
+        mocker.patch("json.load", side_effect=PermissionError("Permission denied"))
+
+        # Should not crash, should handle the error gracefully
+        memory.add_message("testuser", "user", "Second message")
+
+    def test_add_message_handles_write_error_gracefully(self, temp_dir, mocker):
+        """Test that add_message handles file write errors gracefully"""
+        memory = ConversationMemory(data_dir=str(temp_dir))
+
+        # Mock json.dump to raise an exception
+        mocker.patch("json.dump", side_effect=IOError("Disk full"))
+
+        # Should not crash even when write fails
+        memory.add_message("testuser", "user", "Test message")
+
+    def test_clear_user_history_handles_permission_error(self, temp_dir, mocker):
+        """Test that clear_user_history handles permission errors gracefully"""
+        memory = ConversationMemory(data_dir=str(temp_dir))
+
+        # Create a user file
+        memory.add_message("testuser", "user", "Test message")
+
+        # Mock unlink to raise permission error
+        mocker.patch("pathlib.Path.unlink", side_effect=PermissionError("Permission denied"))
+
+        # Should not crash
+        memory.clear_user_history("testuser")