test: add integration and E2E test infrastructure

- Add pytest markers (integration, e2e, slow) with skip logic
- Add command line options (--run-integration, --run-e2e)
- Create sample_project and sample_project_with_bug fixtures
- Add test_integration.py with 10 LLM tests
- Add test_e2e.py with 12 API server tests
- Update COVERAGE.md to reflect ~65% complete

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

webber-api/pyproject.toml

@@ -27,7 +27,15 @@ include = ["src*"]
 testpaths = ["tests"]
 python_files = ["test_*.py"]
 python_functions = ["test_*"]
-addopts = "-v"
+addopts = "-v --strict-markers"
+markers = [
+    "integration: marks tests as integration tests (require Ollama to be running)",
+    "e2e: marks tests as end-to-end tests (require API server to be running)",
+    "slow: marks tests as slow (may take > 10 seconds)",
+]
+filterwarnings = [
+    "ignore::pytest.PytestUnraisableExceptionWarning",
+]
 
 [tool.mypy]
 python_version = "3.12"