refactor: Separate CLI presentation from core business logic

Complete architectural separation of concerns implementing clean layered design:

• Services Layer: Pure business logic isolated from presentation
  - WorkspaceService: TDD workspace operations
  - IssueService: Issue management and creation
  - ProjectService: Project management and milestones
  - ExportService: Unix-friendly data export

• CLI Layer: Clean presentation with command/presenter separation
  - Commands delegate to services for all business operations
  - Presenters handle formatted output and error messaging
  - Framework provides unified interface

• Benefits:
  - Eliminates mixed concerns in 943-line CLI monolith
  - Enables easier testing and maintenance
  - Preserves all existing functionality and Unix pipeline compatibility
  - Provides foundation for future CLI development

Resolves issue #20: CLI separation from core logic

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

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

services/project_service.py

@@ -0,0 +1,76 @@
+"""
+Project service - business logic for project management operations.
+"""
+
+from typing import List, Dict, Any
+
+from tddai.project_manager import ProjectManager, ProjectState, Priority, Milestone, Label
+from tddai import TddaiError
+
+
+class ProjectService:
+    """Service for project management operations."""
+
+    def __init__(self):
+        self.project_manager = ProjectManager()
+
+    def setup_project_management(self) -> None:
+        """Setup project management labels and structure."""
+        self.project_manager.ensure_project_labels()
+
+    def create_milestone(self, title: str, description: str = "", due_date: str = None) -> Milestone:
+        """Create a new milestone (project)."""
+        return self.project_manager.create_milestone(title, description, due_date)
+
+    def list_milestones(self, state: str = "open") -> List[Milestone]:
+        """List milestones."""
+        return self.project_manager.list_milestones(state)
+
+    def list_labels(self) -> List[Label]:
+        """List repository labels."""
+        return self.project_manager.list_labels()
+
+    def set_issue_state(self, issue_number: int, state_name: str) -> Dict[str, Any]:
+        """Set issue project state."""
+        # Convert string to ProjectState enum
+        state_map = {
+            'todo': ProjectState.TODO,
+            'active': ProjectState.ACTIVE,
+            'review': ProjectState.REVIEW,
+            'done': ProjectState.DONE,
+            'blocked': ProjectState.BLOCKED
+        }
+
+        if state_name not in state_map:
+            raise TddaiError(f"Invalid state '{state_name}'. Valid states: {list(state_map.keys())}")
+
+        project_state = state_map[state_name]
+        return self.project_manager.set_issue_state(issue_number, project_state)
+
+    def set_issue_priority(self, issue_number: int, priority_name: str) -> Dict[str, Any]:
+        """Set issue priority."""
+        # Convert string to Priority enum
+        priority_map = {
+            'low': Priority.LOW,
+            'medium': Priority.MEDIUM,
+            'high': Priority.HIGH,
+            'critical': Priority.CRITICAL
+        }
+
+        if priority_name not in priority_map:
+            raise TddaiError(f"Invalid priority '{priority_name}'. Valid priorities: {list(priority_map.keys())}")
+
+        priority_level = priority_map[priority_name]
+        return self.project_manager.set_issue_priority(issue_number, priority_level)
+
+    def move_issue_to_done(self, issue_number: int) -> Dict[str, Any]:
+        """Move issue to done state and close it."""
+        return self.project_manager.move_issue_to_done(issue_number)
+
+    def assign_issue_to_milestone(self, issue_number: int, milestone_id: int) -> Dict[str, Any]:
+        """Assign issue to a milestone."""
+        return self.project_manager.assign_issue_to_milestone(issue_number, milestone_id)
+
+    def get_project_overview(self) -> Dict[str, Any]:
+        """Get project management overview."""
+        return self.project_manager.get_project_overview()