chore: Remove client-specific docs, fix linter errors, update documentation

- Remove SPYKE-related client documentation files
- Fix critical ruff linter errors:
  - Remove unused 'os' import in test_analyze_e2e.py
  - Remove unused 'setups' variable in test_test_example_extractor.py
  - Prefix unused output_dir parameter with underscore in codebase_scraper.py
  - Fix import sorting in test_integration.py
- Update CHANGELOG.md with comprehensive C3.9 and enhancement features
- Update CLAUDE.md with --enhance-level documentation

All critical code quality issues resolved.

src/skill_seekers/cli/codebase_scraper.py

@@ -1572,8 +1572,12 @@ def _format_config_section(output_dir: Path) -> str:
     return content
 
 
-def _format_documentation_section(output_dir: Path, docs_data: dict[str, Any]) -> str:
-    """Format project documentation section from extracted markdown files."""
+def _format_documentation_section(_output_dir: Path, docs_data: dict[str, Any]) -> str:
+    """Format project documentation section from extracted markdown files.
+
+    Note: output_dir parameter is unused but kept for consistency with other _format_* functions.
+    Documentation data is provided via docs_data parameter.
+    """
     if not docs_data or docs_data.get("total_files", 0) == 0:
         return ""