docs: update CHANGELOG for v0.9.0 plugin infrastructure release

Major version 0.9.0 release documenting the complete plugin infrastructure
implementation that enables JavaScript-first development.

**Added:**
- Plugin Infrastructure Foundation with RenderingEnginePlugin system
- TestDrive JSUI Plugin for independent JavaScript UI development
- CLI Engine Parameter (--engine) with intelligent defaults
- Automatic Asset Deployment to _markitect/plugins/ structure
- Complete JavaScript-Python separation with JSON configuration

**Changed:**
- BREAKING: Edit mode now defaults to testdrive-jsui plugin
- Asset management now automatic (no --ship-assets flag needed)
- JavaScript architecture fully modularized with clean separation

**Fixed:**
- JavaScript const redeclaration and loading conflicts resolved
- Plugin asset deployment and accessibility issues fixed

**Migration Guide:**
- Existing users automatically get new testdrive-jsui for edit mode
- Legacy behavior available with --engine standard
- Assets deploy automatically to output directories

This represents the largest architectural enhancement to date, enabling
independent JavaScript development while maintaining clean integration
with the Python markdown processing pipeline.

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

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

CHANGELOG.md

@@ -7,22 +7,43 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [0.9.0] - 2025-11-14
+
 ### Added
+- **Plugin Infrastructure Foundation**: Extended existing MarkiTect plugin system with RenderingEnginePlugin base class and RENDERING plugin type
+- **RenderingEngineManager**: Complete plugin discovery and lifecycle management system for UI rendering engines
+- **RenderingConfig System**: Asset management and deployment configuration for plugin engines
+- **TestDrive JSUI Plugin**: Complete independent JavaScript UI plugin extracted from core system with standalone development environment
+- **Modular Component Architecture**: Compass-positioned controls with clean JSON configuration interface for Python-JavaScript data transfer
+- **CLI Engine Parameter**: Added --engine parameter to markitect md-render command with engine validation and mode compatibility checking
+- **Automatic Asset Deployment**: Production-ready asset deployment to _markitect/plugins/ structure with 18 total assets (12 JS, 3 CSS, 3 images)
 - **ChatGPT Document Theme**: New document theme with Inter font, 580px width, and #10a37f accent color with full CLI support (`markitect md-render --theme chatgpt`)
 - **Modular Theme System Architecture**: File-based theme loading with YAML configuration and dynamic theme discovery
 - **Theme Directory Structure**: Organized theme components (mode/, ui/, document/, branding/) for better maintainability
 - **Database Architecture Documentation**: Comprehensive WORKSPACE_AND_DATABASES.md documenting workspace concepts and database purposes
 
 ### Changed
+- **BREAKING**: Edit mode now defaults to testdrive-jsui plugin instead of legacy edit mode
+- **Default Rendering Behavior**: testdrive-jsui for edit/insert modes, standard for view mode with graceful fallback
+- **Asset Management Strategy**: Automatic plugin asset deployment eliminates need for manual --ship-assets flag
+- **JavaScript Architecture**: Clean separation between Python backend and JavaScript frontend with modular design
 - **Theme Loading System**: Implemented dynamic theme discovery and loading with metadata preservation
 - **Test Suite Organization**: Removed obsolete configuration CLI tests (490 lines) for cleaner codebase
 
 ### Fixed
+- **JavaScript Loading Conflicts**: Resolved const redeclaration errors with MARKITECT_STRICT_MODE implementation
+- **MarkitectMain Availability**: Fixed proper main-updated.js loading and JavaScript syntax errors
+- **Plugin Asset Deployment**: Directory structure preservation with development vs production deployment strategies
 - **Issue-facade Click Framework Bug**: Resolved Sentinel bug in list command that was causing CLI failures
 - **Issue-facade Version Command**: Fixed installation error preventing version command from working
 - **Test Isolation Issues**: Improved test isolation with proper mocking to prevent cross-test interference
 - **Theme Color Assertions**: Updated test assertions to work with new modular theme system
 
+### Migration Guide
+- **Existing Users**: Edit mode will automatically use new testdrive-jsui plugin for enhanced experience
+- **Legacy Behavior**: Use `markitect md-render --engine standard --edit` to access previous edit mode
+- **Asset Deployment**: Plugin assets now deploy automatically - no manual --ship-assets flag required
+
 ## [0.8.0] - 2025-11-08
 
 ### Added
@@ -189,7 +210,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - **Build System**: Enhanced build targets with venv Python and PYTHONPATH support
 - **Target Naming**: Renamed workspace targets to TDD Workspace with tdd- prefix
 
-[Unreleased]: https://github.com/worsch/markitect/compare/v0.8.0...HEAD
+[Unreleased]: https://github.com/worsch/markitect/compare/v0.9.0...HEAD
+[0.9.0]: https://github.com/worsch/markitect/compare/v0.8.0...v0.9.0
 [0.8.0]: https://github.com/worsch/markitect/compare/v0.7.0...v0.8.0
 [0.7.0]: https://github.com/worsch/markitect/compare/v0.6.0...v0.7.0
 [0.6.0]: https://github.com/worsch/markitect/compare/v0.5.0...v0.6.0