Fix racy import validation in duplicate detection test

setValue types character-by-character, firing async validation on each
keystroke. On slow runners, a validation for partial text can resolve
after the final one, showing "1 invalid" instead of "1 duplicate".
Set the value directly and dispatch a single input event instead.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: richardkmichael

tests/firefox/extension.spec.js

@@ -205,8 +205,16 @@ describe('Popup', function () {
     const importBtn = await $('#import-btn');
     await importBtn.click();
 
+    // Set value directly and dispatch a single input event, rather than using
+    // setValue which types character-by-character. Each keystroke triggers async
+    // validation — on slow runners, a validation for partial text can resolve
+    // after the final one, producing "1 invalid" instead of "1 duplicate".
     const textarea = await $('#import-textarea');
-    await textarea.setValue(`- ${issueUrl(TEST_ISSUES[0])}`);
+    const pasteText = `- ${issueUrl(TEST_ISSUES[0])}`;
+    await browser.execute(function (el, text) {
+      el.value = text;
+      el.dispatchEvent(new Event('input', { bubbles: true }));
+    }, textarea, pasteText);
     await browser.pause(500);
 
     const validation = await $('#import-validation');