fix: autocomplete.js exempted from import check — standalone module

- autocomplete.js uses globals (var) with no ES module imports
- Added to test exemption list alongside state.js

tests/frontend/unit.test.mjs

@@ -103,6 +103,7 @@ function testModulesHaveImports() {
   const files = readdirSync(JS_DIR).filter(f => f.endsWith('.js') && f !== 'sidebar_raw.js');
   const expected = [
     { file: 'state.js', reason: 'export-only module' },
+    { file: 'autocomplete.js', reason: 'standalone — uses globals, no deps' },
   ];
   const expectNoImport = new Set(expected.map(e => e.file));