fix: fix remaining .js imports in test assertions and type exports

- Convert remaining .js -> .ts in test file imports
- Revert .ts back to .js in test assertion strings (expectIncludes)
- Fix GetOutputHTMLParams type-only import

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

Author: bennypowers

packages/dev-server-rollup/test/node/plugins/alias.test.ts

@@ -20,7 +20,7 @@ describe('@rollup/plugin-alias', () => {
 
     try {
       const text = await fetchText(`${host}/app.js`);
-      expectIncludes(text, "import moduleA from './module-a-stub.ts'");
+      expectIncludes(text, "import moduleA from './module-a-stub.js'");
     } finally {
       server.stop();
     }

packages/dev-server-rollup/test/node/plugins/node-resolve.test.ts

@@ -19,7 +19,7 @@ describe('@rollup/plugin-node-resolve', () => {
 
     try {
       const text = await fetchText(`${host}/app.js`);
-      expectIncludes(text, "import moduleA from './node_modules/module-a/index.ts'");
+      expectIncludes(text, "import moduleA from './node_modules/module-a/index.js'");
     } finally {
       server.stop();
     }

packages/dev-server-rollup/test/node/plugins/postcss.test.ts

@@ -51,7 +51,7 @@ html {
       expectIncludes(text, 'export default');
       expectIncludes(
         text,
-        "import styleInject from './node_modules/style-inject/dist/style-inject.es.ts';",
+        "import styleInject from './node_modules/style-inject/dist/style-inject.es.js';",
       );
       expectIncludes(text, 'styleInject(css_248z);');
     } finally {

packages/rollup-plugin-html/test/src/output/getOutputHTML.test.ts

@@ -1,7 +1,7 @@
 import { expect } from 'chai';
 import path from 'path';
-import { getOutputHTML, GetOutputHTMLParams } from '../../../src/output/getOutputHTML.js';
-import type { EntrypointBundle } from '../../../src/RollupPluginHTMLOptions.js';
+import { getOutputHTML, type GetOutputHTMLParams } from '../../../src/output/getOutputHTML.js';
+import { EntrypointBundle } from '../../../src/RollupPluginHTMLOptions.js';
 import { html } from '../../utils.js';
 
 describe('getOutputHTML()', () => {