docs: add ProjectDiary entry for TDD infrastructure implementation

- Document complete tddai Python library implementation
- Summarize key achievements: 5 core modules, CLI interface, 20 passing tests
- Record transition from shell-based to Python library architecture
- Note tdd- prefix renaming and proper TDD green-state practices
- Estimate 3-4 hours development time with ~100K AI tokens used
- Maintain reverse chronological order for diary entries

This completes the documentation of the major TDD infrastructure milestone.

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

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

ProjectDiary.md

@@ -4,6 +4,17 @@ This diary tracks major work packages, events, and milestones in the MarkiTect p
 
 ---
 
+## 2025-09-22: TDD Infrastructure Implementation & Python Library Architecture
+
+**Progress:** Complete TDD workspace infrastructure with robust Python library implementation
+**Contributors:** User (bernd.worsch), Claude Code (Sonnet 4)
+**Time Estimate:** ~3-4 hours of active development
+**AI Resources:** ~30-40 Claude Sonnet 4 conversations, estimated 100K+ tokens
+
+Successfully implemented comprehensive TDD workspace infrastructure by creating the `tddai` Python library to replace complex shell-based Makefile logic. Key achievements include a complete Python package architecture with workspace management, Gitea API integration, and AI-assisted test generation capabilities. Created five core modules: workspace lifecycle management, issue fetching with error handling, test generation framework, environment-based configuration, and custom exception hierarchy. Built Python CLI interface (`tddai_cli.py`) that provides clean command-line access to all TDD operations. Updated Makefile to use Python CLI with proper virtual environment integration and PYTHONPATH configuration. Developed comprehensive test suite with 20 passing tests using pytest, including behavior-based testing with proper mocking and fixtures. Implemented complete TDD workflow from issue-to-workspace creation, iterative test addition, workspace status monitoring, and final integration with cleanup. Renamed targets to use `tdd-` prefix for clarity: `tdd-start`, `tdd-add-test`, `tdd-status`, `tdd-finish`. All functionality achieved green test state before committing, demonstrating proper TDD practices. This establishes a maintainable, extensible foundation for issue-driven development with AI assistance.
+
+---
+
 ## 2025-09-22: Repository Infrastructure & Development Workflow Establishment
 
 **Progress:** Comprehensive development infrastructure setup with automated workflows