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/subsystem-compile/_skill.json

@@ -8,5 +8,6 @@
   "snapshot": {
     "root": "workDir",
     "normalizeUuids": true
-  }
+  },
+  "postValidate": { "script": "subsystem-validate/scripts/subsystem-validate", "flag": "-SubsystemPath", "pathFrom": "validatePath" }
 }