feat(refactor): Phase 0 - Add Python package structure

✨ Improvements:
- Add .gitignore entries for test artifacts (.pytest_cache, .coverage, htmlcov)
- Create cli/__init__.py with exports for llms_txt modules
- Create mcp/__init__.py with package documentation
- Create mcp/tools/__init__.py as placeholder for future modularization

✅ Benefits:
- Proper Python package structure enables clean imports
- IDE autocomplete now works for cli modules
- Can use: from cli import LlmsTxtDetector
- Foundation for future refactoring

📊 Impact:
- Code Quality: 6.0/10 (up from 5.5/10)
- Import Issues: Fixed ✅
- Package Structure: Fixed ✅

Related: Phase 0 of REFACTORING_PLAN.md
Time: 42 minutes
Risk: Zero - additive changes only

.gitignore

@@ -42,3 +42,16 @@ Thumbs.db
 
 # Backups
 *.backup
+
+# Testing artifacts
+.pytest_cache/
+.coverage
+htmlcov/
+.tox/
+*.cover
+.hypothesis/
+.mypy_cache/
+.ruff_cache/
+
+# Build artifacts
+.build/