Update to Lit 2.0.0 (manually)

Will attempt to get this back to syncing with monorepo history per https://github.com/lit/lit#exporting-starter-templates in a follow-up.

web-test-runner.config.js

@@ -7,6 +7,11 @@
 import {legacyPlugin} from '@web/dev-server-legacy';
 import {playwrightLauncher} from '@web/test-runner-playwright';
 
+const mode = process.env.MODE || 'dev';
+if (!['dev', 'prod'].includes(mode)) {
+  throw new Error(`MODE must be "dev" or "prod", was "${mode}"`);
+}
+
 // Uncomment for testing on Sauce Labs
 // Must run `npm i --save-dev @web/test-runner-saucelabs` and set
 // SAUCE_USERNAME and SAUCE_USERNAME environment variables
@@ -87,7 +92,7 @@ try {
 export default {
   rootDir: '.',
   files: ['./test/**/*_test.js'],
-  nodeResolve: true,
+  nodeResolve: {exportConditions: mode === 'dev' ? ['development'] : []},
   preserveSymlinks: true,
   browsers: commandLineBrowsers ?? Object.values(browsers),
   testFramework: {
@@ -108,8 +113,7 @@ export default {
           {
             name: 'lit-polyfill-support',
             path: 'node_modules/lit/polyfill-support.js',
-            test:
-              "!('attachShadow' in Element.prototype) || !('getRootNode' in Element.prototype) || window.ShadyDOM && window.ShadyDOM.force",
+            test: "!('attachShadow' in Element.prototype) || !('getRootNode' in Element.prototype) || window.ShadyDOM && window.ShadyDOM.force",
             module: false,
           },
         ],