Add a Playwright test for activating a quick bar mod without the quickbar shortcut configured

[mnholtz]

Create a Playwright test that effectively replaces the manual regression checklist test "Activating a quick bar mod when you don’t have a quick bar shortcut configured" under the "Extension Console Activation" test group: https://www.notion.so/pixiebrix/Release-Checklist-Template-6d435dbf9a464f119ac6202b05d9c3b5?pvs=4#3afe7c8fc2f84c70a6ab86a8b5c1bcc0

Acceptance Criteria Add a Playwright test that:

• Activates a quickbar mod (e.g. @pixies/hn/search-quickback without the quickbar shortcut configured (you may need to visit the Extensions page to remove the shortcut configuration)
• Verify that the activated mod works in https://pbx.vercel.app/
• After merging, remove the test from the regression checklist notion template https://www.notion.so/pixiebrix/Release-Checklist-Template-6d435dbf9a464f119ac6202b05d9c3b5?pvs=4#3afe7c8fc2f84c70a6ab86a8b5c1bcc0