fix(adapter-vite): customElements.define(tagName) counts as tagName usage in the scanner

Routes registering via the platform primitive (www, the reference starter)
were misread as orphaned tagName exports and drew the #960 migration note
on every build. The usage detector now recognizes both defineElement and
customElements.define, with a pin test.

Author: DevBot

packages/adapter-vite/__tests__/route-scanner-tagname.test.ts

@@ -189,6 +189,33 @@ export default definePage({
   }
 });
 
+Deno.test('scanRoutes treats customElements.define(tagName) as usage (no orphan note)', async () => {
+  const dir = await Deno.makeTempDir({ prefix: 'oe-scan-tagname-' });
+  try {
+    const routesDir = join(dir, 'routes');
+    await Deno.mkdir(routesDir, { recursive: true });
+    // The www site and some starters register via the platform primitive
+    // instead of defineElement — that is still a use of the export.
+    await Deno.writeTextFile(
+      join(routesDir, 'home.tsx'),
+      `import { definePage } from '@openelement/app';
+export const tagName = 'page-home';
+class HomePage extends HTMLElement {}
+customElements.define(tagName, HomePage);
+export default definePage({ render() { return <page-home />; } });
+`,
+    );
+
+    const messages = await captureInfo(async () => {
+      await scanRoutes(routesDir);
+    });
+    const notes = messages.filter((m) => m.includes('ignored for registration'));
+    assertEquals(notes, [], 'customElements.define(tagName) must count as usage');
+  } finally {
+    await Deno.remove(dir, { recursive: true }).catch(() => {});
+  }
+});
+
 Deno.test('scanRoutes notes an orphaned tagName export on a definePage route once', async () => {
   const dir = await Deno.makeTempDir({ prefix: 'oe-scan-decouple-' });
   try {

packages/adapter-vite/src/internal/ssg/route-scanner.ts

@@ -211,8 +211,14 @@ function escapeRegExp(value: string): string {
  * an embedded code sample merely suppresses the note (the safe direction).
  */
 function routeUsesTagName(source: string, tagName: string): boolean {
-  if (/\bdefineElement\s*\(\s*tagName\b/.test(source)) return true;
-  if (new RegExp(`\\bdefineElement\\s*\\(\\s*['"\`]${escapeRegExp(tagName)}['"\`]`).test(source)) {
+  // defineElement(tagName, …) or customElements.define(tagName, …) — the
+  // www site and some starters register via the platform primitive.
+  if (/\b(?:defineElement|customElements\.define)\s*\(\s*tagName\b/.test(source)) return true;
+  if (
+    new RegExp(
+      `\\b(?:defineElement|customElements\\.define)\\s*\\(\\s*['"\`]${escapeRegExp(tagName)}['"\`]`,
+    ).test(source)
+  ) {
     return true;
   }
   return new RegExp(`</?${escapeRegExp(tagName)}(?=[\\s/>])`).test(source);