Scope CI retries: 2 for Navigation (live github.com), 1 globally

Navigation tests hit live github.com and are subject to runner and
network variability. Other tests use local moz-extension:// pages
and get 1 retry for intermittent BiDi flakiness only.

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

Author: richardkmichael

tests/firefox/extension.spec.js

@@ -200,6 +200,7 @@ describe('Popup', function () {
 
     await browser.url(popupUrl());
     await waitForPopupLoaded();
+    await $('.issue-item').waitForDisplayed({ timeout: 10000 });
 
     const importBtn = await $('#import-btn');
     await importBtn.click();
@@ -399,6 +400,7 @@ describe('Options', function () {
 
 describe('Navigation', function () {
   this.timeout(30000);
+  this.retries(process.env.CI ? 2 : 0);
 
   const bookmarkSelector = '[data-extension-bookmark]';
   const headerActionsSelector = '[data-component="PH_Actions"]';