docs: remove common-cache references from documentation and tooling

Remove all remaining references to common-cache from project documentation,
test workflows, and build tooling after action deletion.

Updated:
- CLAUDE.md: Remove from action catalog (28 → 27 actions)
- README.md: Regenerate catalog without common-cache
- SECURITY.md: Update caching optimization notes
- Test workflows: Remove common-cache test references
- spec_helper.sh: Remove common-cache test helpers
- generate_listing.cjs: Remove from category/language mappings
- update-validators.py: Remove custom validator entry

validate-inputs/scripts/update-validators.py

@@ -304,10 +304,6 @@ class ValidationRuleGenerator:
                 "cache-mode": "cache_mode",
                 "sbom-format": "sbom_format",
             },
-            "common-cache": {
-                "paths": "file_path",
-                "key-files": "file_path",
-            },
             "common-file-check": {
                 "file-pattern": "file_path",
             },