feat: post-run validation + integration tests for skill pipeline

- runner.mjs v0.4: --with-validation flag runs validators on real output
- postValidate config in 20 _skill.json files (maps skill → validator)
- validatePath in ~100 positive test cases
- skipValidation for 5 cross-reference cases (isolated workspace limitation)
- Integration tests: build-config (19 steps), build-epf (6), build-cfe (4)
- base-config cache from build-config for downstream tests
- Fix chart-of-calculation-types test data (DependenceOnCalculationTypes)
- 285/285 unit + 3/3 integration, all green with validation

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/skills/cases/mxl-compile/format-strings.json

@@ -34,6 +34,7 @@
     ]
   },
   "params": { "outputPath": "Template.xml" },
+  "validatePath": "Template.xml",
   "expect": {
     "files": ["Template.xml"]
   }