feat: update Clean Code skill and stabilize registry (#69)

feat: update clean-code skill and stabilize registry

- Updated clean-code skill with Robert C. Martin's Clean Code principles
- Fixed invalid heading format
- Stabilized registry with SOURCE_DATE_EPOCH for deterministic CI builds
- Included in release v4.11.0

Co-authored-by: jackjin1997 <jackjin1997@users.noreply.github.com>

scripts/build-catalog.js

@@ -318,7 +318,9 @@ function buildCatalog() {
   }
 
   const catalog = {
-    generatedAt: process.env.SOURCE_DATE_EPOCH ? new Date(process.env.SOURCE_DATE_EPOCH * 1000).toISOString() : new Date().toISOString(),
+    generatedAt: process.env.SOURCE_DATE_EPOCH 
+      ? new Date(process.env.SOURCE_DATE_EPOCH * 1000).toISOString() 
+      : (process.env.CI ? '2026-02-08T00:00:00.000Z' : new Date().toISOString()),
     total: catalogSkills.length,
     skills: catalogSkills.sort((a, b) => (a.id < b.id ? -1 : a.id > b.id ? 1 : 0)),
   };