fix(deps): replace step-security/retry and update action pins (#468)

* fix(deps): replace step-security/retry with nick-fields/retry

* chore(deps): update github action sha pins via pinact

* refactor: remove common-retry references from tests and validators

* chore: simplify description fallback and update action count

* docs: remove hardcoded test counts from memory and docs

Replace exact "769 tests" references with qualitative language
so these files don't go stale as test count grows.

.serena/memories/validator_system.md

@@ -2,7 +2,7 @@
 
 ## Status: PRODUCTION READY ✅
 
-- 769 tests passing (100%)
+- All tests passing (100%)
 - Zero linting issues
 - Modular architecture complete
 
@@ -60,7 +60,7 @@ validate-inputs/
 ├── scripts/
 │   ├── update-validators.py  # Rule generator
 │   └── generate-tests.py     # Test generator
-└── tests/                    # 769 pytest tests
+└── tests/                    # pytest tests
 
 <action>/CustomValidator.py   # Action-specific validators
 ```