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/__init__.py

@@ -0,0 +1,28 @@
+"""
+Business logic services layer.
+
+This package contains pure business logic services that are independent of
+CLI presentation concerns. Services focus on:
+
+- Core business operations
+- Data transformation
+- Validation and error handling
+- Integration with lower-level modules
+
+Services should NOT:
+- Handle CLI arguments directly
+- Print output or format data for display
+- Call sys.exit() or handle CLI-specific errors
+"""
+
+from .workspace_service import WorkspaceService
+from .issue_service import IssueService
+from .project_service import ProjectService
+from .export_service import ExportService
+
+__all__ = [
+    'WorkspaceService',
+    'IssueService',
+    'ProjectService',
+    'ExportService'
+]