Speed up npm run test with eslint/tsc caching

Ignore .agents skill bundles from eslint (template files not part of
the build), enable eslint --cache and tsc --incremental so warm re-runs
skip unchanged files.

eslint.config.js

@@ -8,7 +8,7 @@ import htmlParser from "@html-eslint/parser";
 import customRules from "./eslint-rules/index.js";
 
 export default tseslint.config(
-  { ignores: ["dist", "android", "ios"] },
+  { ignores: ["dist", "android", "ios", ".agents"] },
   {
     extends: [js.configs.recommended, ...tseslint.configs.recommended],
     files: ["**/*.{ts,tsx}"],