Add Kiro provider support, clean up legacy code and unused ZIPs

- Add Kiro transformer and build integration (.kiro/skills/ structure)
- Add Kiro to validation allowlists, API handlers, and homepage badge
- Replace legacy getFilePath in Vercel API with unified skills directory structure
- Remove individual provider ZIP creation (only universal ZIPs needed)
- Simplify bundle API allowlist to universal/universal-prefixed only

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

scripts/lib/utils.js

@@ -288,6 +288,11 @@ export const PROVIDER_PLACEHOLDERS = {
     model: 'the model',
     config_file: '.github/copilot-instructions.md',
     ask_instruction: 'ask the user directly to clarify what you cannot infer.'
+  },
+  'kiro': {
+    model: 'Claude',
+    config_file: '.kiro/settings.json',
+    ask_instruction: 'ask the user directly to clarify what you cannot infer.'
   }
 };