feat: implement configuration and environment management CLI (issue #18)

Complete implementation of configuration management capabilities for MarkiTect CLI:

New CLI Commands:
- markitect config-show: Display current configuration with multiple output formats
- markitect config-set: Set configuration values with validation and persistence
- markitect config-init: Initialize configuration for new project with interactive setup
- markitect config-validate: Validate current configuration and show issues
- markitect config-help: Get help information for configuration keys

Core Features:
- Comprehensive configuration management with multiple sources (files, env vars, defaults)
- Support for YAML, JSON, and simple output formats
- Sensitive data masking for secure configuration display
- Interactive project initialization with intelligent defaults
- Configuration validation with path creation and URL validation
- Environment variable integration with MARKITECT_ prefix
- Nested configuration support with dot notation (e.g., gitea.url)
- Type conversion for boolean, numeric, and string values
- Project-specific configuration files (.markitect.yml/yaml/json)

Technical Implementation:
- ConfigurationManager class with robust error handling
- Integration with existing configuration system
- File-based configuration with automatic format detection
- Configuration validation and help system
- Support for custom configuration file locations
- Graceful fallback when advanced config system unavailable

Configuration Features:
- Multiple file format support (YAML, JSON)
- Environment variable precedence
- Sensitive data protection
- Directory structure validation and creation
- URL and path validation
- Interactive and non-interactive modes

Testing:
- 58 comprehensive tests covering all functionality
- CLI integration tests with isolated environments
- Edge cases: permissions, invalid paths, complex structures
- Configuration file parsing and saving tests
- Environment variable handling tests
- Validation and error handling scenarios

All acceptance criteria fulfilled:
✅ Configuration display and management
✅ Project initialization functionality
✅ Configuration validation
✅ Integration with existing config system
✅ Comprehensive test coverage

🤖 Generated with [Claude Code](https://claude.ai/code)

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

markitect/cli.py

@@ -29,6 +29,7 @@ from .database import DatabaseManager
 from .legacy_compat import LegacyMode, emit_deprecation_warning, legacy_switch_option
 from .__version__ import get_version_info, get_release_info
 from .batch_processor import BatchProcessor, ProcessingMode, ErrorHandling, create_file_processor
+from .config_manager import ConfigurationManager
 
 # Import legacy system components for advanced management
 try:
@@ -4744,6 +4745,301 @@ def recursive(config, directory, depth, operation, pattern, error_handling, quie
         sys.exit(1)
 
 
+# Configuration Management Commands - Issue #18
+
+
+@cli.command(name='config-show')
+@click.option('--format', 'output_format', type=click.Choice(['yaml', 'json', 'simple']),
+              default='yaml', help='Output format for configuration display')
+@click.option('--show-sensitive', is_flag=True, help='Show sensitive values (tokens, passwords)')
+@pass_config
+def config_show(config, output_format, show_sensitive):
+    """Display current configuration.
+
+    Shows comprehensive configuration information including current settings,
+    file sources, environment variables, and workspace information.
+
+    Examples:
+        markitect config-show
+        markitect config-show --format json
+        markitect config-show --format simple --show-sensitive
+    """
+    try:
+        config_manager = ConfigurationManager()
+        output = config_manager.display_config(
+            show_sensitive=show_sensitive,
+            output_format=output_format
+        )
+        click.echo(output)
+
+    except Exception as e:
+        click.echo(f"Failed to display configuration: {e}", err=True)
+        if config.get('verbose'):
+            import traceback
+            click.echo(traceback.format_exc(), err=True)
+        sys.exit(1)
+
+
+@cli.command(name='config-set')
+@click.argument('key', type=str)
+@click.argument('value', type=str)
+@click.option('--config-file', type=click.Path(), help='Target configuration file')
+@click.option('--validate/--no-validate', default=True, help='Validate configuration after setting')
+@pass_config
+def config_set(config, key, value, config_file, validate):
+    """Set configuration values.
+
+    Sets a configuration value and persists it to a configuration file.
+    Supports nested keys using dot notation (e.g., 'gitea.url').
+
+    Examples:
+        markitect config-set gitea_url http://localhost:3000
+        markitect config-set repo_owner myorganization
+        markitect config-set api_token abc123def456
+        markitect config-set workspace.dir ./my_workspace
+    """
+    try:
+        config_manager = ConfigurationManager()
+
+        # Set the configuration value
+        success = config_manager.set_config_value(key, value, config_file)
+
+        if success:
+            click.echo(f"✅ Configuration updated: {key} = {value}")
+
+            # Show which file was updated
+            target_file = config_manager._get_target_config_file(config_file)
+            click.echo(f"📁 Updated file: {target_file}")
+
+            # Validate configuration if requested
+            if validate:
+                validation_results = config_manager.validate_configuration()
+                errors = [r for r in validation_results if r['status'] == 'error']
+                if errors:
+                    click.echo("⚠️  Configuration validation warnings:")
+                    for error in errors:
+                        click.echo(f"   • {error['key']}: {error['message']}")
+
+        else:
+            click.echo(f"❌ Failed to set configuration: {key}", err=True)
+            sys.exit(1)
+
+    except ValueError as e:
+        click.echo(f"❌ Configuration error: {e}", err=True)
+        sys.exit(1)
+    except Exception as e:
+        click.echo(f"❌ Failed to set configuration: {e}", err=True)
+        if config.get('verbose'):
+            import traceback
+            click.echo(traceback.format_exc(), err=True)
+        sys.exit(1)
+
+
+@cli.command(name='config-init')
+@click.option('--project-dir', type=click.Path(path_type=Path), help='Target project directory')
+@click.option('--interactive/--no-interactive', default=True, help='Interactive configuration setup')
+@click.option('--force', is_flag=True, help='Overwrite existing configuration')
+@pass_config
+def config_init(config, project_dir, interactive, force):
+    """Initialize configuration for new project.
+
+    Creates a new configuration file with sensible defaults and sets up
+    the necessary directory structure for a MarkiTect project.
+
+    Examples:
+        markitect config-init
+        markitect config-init --project-dir ./my-project
+        markitect config-init --no-interactive --force
+    """
+    try:
+        target_dir = project_dir or Path.cwd()
+        config_file = target_dir / '.markitect.yml'
+
+        # Check if configuration already exists
+        if config_file.exists() and not force:
+            click.echo(f"❌ Configuration file already exists: {config_file}")
+            click.echo("   Use --force to overwrite or choose a different directory")
+            sys.exit(1)
+
+        config_manager = ConfigurationManager()
+
+        # Interactive setup if requested
+        initial_config = {
+            'gitea_url': 'http://localhost:3000',
+            'repo_owner': '',
+            'repo_name': target_dir.name,
+            'workspace_dir': '.markitect_workspace',
+            'cache_dir': '.ast_cache',
+            'tests_dir': 'tests',
+            'test_file_pattern': 'test_issue_{issue_num}_{scenario}.py',
+            'claude_code_command': 'claude'
+        }
+
+        if interactive:
+            click.echo("🔧 Interactive MarkiTect configuration setup")
+            click.echo(f"📁 Target directory: {target_dir}")
+            click.echo()
+
+            # Prompt for each configuration value
+            initial_config['gitea_url'] = click.prompt(
+                'Gitea server URL',
+                default=initial_config['gitea_url']
+            )
+            initial_config['repo_owner'] = click.prompt(
+                'Repository owner/organization',
+                default=initial_config['repo_owner']
+            )
+            initial_config['repo_name'] = click.prompt(
+                'Repository name',
+                default=initial_config['repo_name']
+            )
+
+            if click.confirm('Configure API token now?', default=False):
+                initial_config['api_token'] = click.prompt(
+                    'API token',
+                    default='',
+                    hide_input=True
+                )
+
+            initial_config['workspace_dir'] = click.prompt(
+                'Workspace directory',
+                default=initial_config['workspace_dir']
+            )
+            initial_config['tests_dir'] = click.prompt(
+                'Tests directory',
+                default=initial_config['tests_dir']
+            )
+
+        # Initialize the project
+        result = config_manager.initialize_project_config(target_dir, interactive=False)
+
+        # Update with interactive values if provided
+        if interactive:
+            config_manager._save_config_file(initial_config, config_file)
+            result['config'] = initial_config
+
+        click.echo("✅ MarkiTect project initialized successfully!")
+        click.echo(f"📄 Configuration file: {result['config_file']}")
+        click.echo("📁 Created directories:")
+        for directory in result['created_directories']:
+            click.echo(f"   • {directory}")
+
+        # Show validation results
+        validation_results = config_manager.validate_configuration(result['config'])
+        warnings = [r for r in validation_results if r['status'] == 'warning']
+        errors = [r for r in validation_results if r['status'] == 'error']
+
+        if warnings:
+            click.echo("⚠️  Configuration warnings:")
+            for warning in warnings:
+                click.echo(f"   • {warning['message']}")
+
+        if errors:
+            click.echo("❌ Configuration errors:")
+            for error in errors:
+                click.echo(f"   • {error['message']}")
+        else:
+            click.echo("🎉 Configuration validation passed!")
+
+    except Exception as e:
+        click.echo(f"❌ Failed to initialize configuration: {e}", err=True)
+        if config.get('verbose'):
+            import traceback
+            click.echo(traceback.format_exc(), err=True)
+        sys.exit(1)
+
+
+@cli.command(name='config-validate')
+@click.option('--verbose', '-v', is_flag=True, help='Show detailed validation information')
+@pass_config
+def config_validate(config, verbose):
+    """Validate current configuration.
+
+    Checks the current configuration for common issues, missing required fields,
+    and validates paths and URLs. Provides suggestions for fixing any problems.
+
+    Examples:
+        markitect config-validate
+        markitect config-validate --verbose
+    """
+    try:
+        config_manager = ConfigurationManager()
+        validation_results = config_manager.validate_configuration()
+
+        # Categorize results
+        errors = [r for r in validation_results if r['status'] == 'error']
+        warnings = [r for r in validation_results if r['status'] == 'warning']
+        ok_results = [r for r in validation_results if r['status'] == 'ok']
+
+        # Display summary
+        click.echo(f"📊 Configuration Validation Summary:")
+        click.echo(f"   ✅ OK: {len(ok_results)}")
+        click.echo(f"   ⚠️  Warnings: {len(warnings)}")
+        click.echo(f"   ❌ Errors: {len(errors)}")
+        click.echo()
+
+        # Show errors
+        if errors:
+            click.echo("❌ Configuration Errors:")
+            for error in errors:
+                click.echo(f"   • {error['key']}: {error['message']}")
+            click.echo()
+
+        # Show warnings
+        if warnings:
+            click.echo("⚠️  Configuration Warnings:")
+            for warning in warnings:
+                click.echo(f"   • {warning['key']}: {warning['message']}")
+            click.echo()
+
+        # Show OK results in verbose mode
+        if verbose and ok_results:
+            click.echo("✅ Valid Configuration:")
+            for ok_result in ok_results:
+                click.echo(f"   • {ok_result['key']}: {ok_result['message']}")
+            click.echo()
+
+        # Overall status
+        if errors:
+            click.echo("❌ Configuration validation failed")
+            sys.exit(1)
+        elif warnings:
+            click.echo("⚠️  Configuration validation passed with warnings")
+        else:
+            click.echo("✅ Configuration validation passed")
+
+    except Exception as e:
+        click.echo(f"❌ Configuration validation failed: {e}", err=True)
+        if config.get('verbose'):
+            import traceback
+            click.echo(traceback.format_exc(), err=True)
+        sys.exit(1)
+
+
+@cli.command(name='config-help')
+@click.argument('key', required=False)
+@pass_config
+def config_help(config, key):
+    """Get help information for configuration keys.
+
+    Provides detailed information about available configuration options,
+    their purposes, and example values.
+
+    Examples:
+        markitect config-help
+        markitect config-help gitea_url
+        markitect config-help api_token
+    """
+    try:
+        config_manager = ConfigurationManager()
+        help_text = config_manager.get_config_help(key)
+        click.echo(help_text)
+
+    except Exception as e:
+        click.echo(f"❌ Failed to get configuration help: {e}", err=True)
+        sys.exit(1)
+
+
 # Register issue management commands
 cli.add_command(issues_group)