feat: implement tddai Python library for TDD workspace management

- Create comprehensive tddai package with workspace, issue fetcher, and test generator modules
- Add Python CLI interface (tddai_cli.py) to replace complex Makefile shell logic
- Update Makefile targets to use Python CLI for better maintainability
- Implement proper behavior-based tests instead of file existence checks
- Add workspace lifecycle management (create, active, finish, cleanup)
- Add issue fetching from Gitea API with error handling
- Add comprehensive test coverage with 19 passing tests
- Support environment variable configuration for different deployments

This addresses issue #11: Setup TDD workspace infrastructure
All tests pass and the system achieves green state before commit.

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

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

tddai/config.py

@@ -0,0 +1,92 @@
+"""
+Configuration management for tddai.
+"""
+
+import os
+from pathlib import Path
+from typing import Optional
+from dataclasses import dataclass
+
+from .exceptions import ConfigurationError
+
+
+@dataclass
+class TddaiConfig:
+    """Configuration settings for tddai."""
+
+    # Workspace settings
+    workspace_dir: Path = Path(".markitect_workspace")
+    current_issue_file: str = "current_issue.json"
+
+    # Git repository settings
+    gitea_url: str = "http://92.205.130.254:32166"
+    repo_owner: str = "coulomb"
+    repo_name: str = "markitect_project"
+
+    # Test settings
+    tests_dir: Path = Path("tests")
+    test_file_pattern: str = "test_issue_{issue_num}_{scenario}.py"
+
+    # AI settings
+    claude_code_command: str = "claude"
+
+    @property
+    def issues_api_url(self) -> str:
+        """Get the full issues API URL."""
+        return f"{self.gitea_url}/api/v1/repos/{self.repo_owner}/{self.repo_name}/issues"
+
+    @property
+    def current_issue_path(self) -> Path:
+        """Get the path to current issue file."""
+        return self.workspace_dir / self.current_issue_file
+
+    @classmethod
+    def from_environment(cls) -> "TddaiConfig":
+        """Create config from environment variables."""
+        config = cls()
+
+        # Override with environment variables if present
+        if gitea_url := os.getenv("TDDAI_GITEA_URL"):
+            config.gitea_url = gitea_url
+
+        if repo_owner := os.getenv("TDDAI_REPO_OWNER"):
+            config.repo_owner = repo_owner
+
+        if repo_name := os.getenv("TDDAI_REPO_NAME"):
+            config.repo_name = repo_name
+
+        if workspace_dir := os.getenv("TDDAI_WORKSPACE_DIR"):
+            config.workspace_dir = Path(workspace_dir)
+
+        return config
+
+    def validate(self) -> None:
+        """Validate configuration settings."""
+        if not self.gitea_url:
+            raise ConfigurationError("gitea_url cannot be empty")
+
+        if not self.repo_owner:
+            raise ConfigurationError("repo_owner cannot be empty")
+
+        if not self.repo_name:
+            raise ConfigurationError("repo_name cannot be empty")
+
+
+# Global config instance
+_config: Optional[TddaiConfig] = None
+
+
+def get_config() -> TddaiConfig:
+    """Get the global configuration instance."""
+    global _config
+    if _config is None:
+        _config = TddaiConfig.from_environment()
+        _config.validate()
+    return _config
+
+
+def set_config(config: TddaiConfig) -> None:
+    """Set the global configuration instance."""
+    global _config
+    config.validate()
+    _config = config