test(rollup-plugin-html): migrate from mocha/chai to node:test

Replace mocha/chai with node:test and node:assert/strict across all 9
test files (139 tests). Update test script to use
node --experimental-strip-types --test. Change source imports to dist
imports and use import type for type-only imports.

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

Author: bennypowers

packages/rollup-plugin-html/package.json

@@ -28,8 +28,7 @@
     "demo:mpa": "rm -rf demo/dist && rollup -c demo/mpa/rollup.config.js --watch & npm run serve-demo",
     "demo:spa": "rm -rf demo/dist && rollup -c demo/spa/rollup.config.js --watch & npm run serve-demo",
     "serve-demo": "node ../dev-server/dist/bin.js --watch --root-dir demo/dist --app-index index.html --compatibility none --open",
-    "test:node": "mocha test/**/*.test.ts --require ts-node/register --reporter dot",
-    "test:watch": "mocha test/**/*.test.ts --require ts-node/register --watch --watch-files src,test"
+    "test:node": "node --experimental-strip-types --test --test-force-exit 'test/**/*.test.ts'"
   },
   "files": [
     "*.js",