Bug: addStarterBrick e2e tests flaky on sidebar ping

[mnholtz]

End to end tests for addStarterBrick are intermittently failing on the Pre-release browser workflow, for both msedge-beta and msedge: https://github.com/pixiebrix/pixiebrix-extension/actions/runs/10381677885/job/28771479311

Tests seem to be failing consistently with the error The Sidebar is taking longer than expected to load. Retrying... when waiting for the sidebar to open.

[grahamlangford]

I spent a day digging into this bug. This only appears to happen when running the e2e tests. When adding a sidepanel starterbrick using the Page Editor, the sidepanel should open automatically, but it doesn't. Nor does the gesture popover appear.

Findings:

• Cannot be replicated in MS Edge outside Playwright
  • Tested with the Page Editor open in another tab to as closely simulate the test as possible and still could not replicate
• Can be replicated in MS Edge launched by Playwright
• When running the e2e test, if I pause test execution as soon as the test had finished starting up, I can replicate in the Playwright-launched Edge browser (same Edge version as when not using Playwright)
• Tested with old versions of the Extension from before the flakiness appeared, but was still able to reproduce in Playwright
• Confirmed that the chrome.sidePanel.open method is being called