Save button doesn't open the save modal sometimes

[fungairino]

Describe the bug

The save button re-mounts several times so we need to retry clicking the saveButton until the modal is visible in end to end tests.

For end users this means that sometimes clicking this button does nothing and they don't know why. This happens most often right after loading the page editor, but also just happens intermittently.

To Reproduce

https://github.com/user-attachments/assets/2a605a16-7e69-4c79-9032-afeb45d9b440

Expected behavior

The save button always works, or is disabled if it is not clickable yet.

Additional context

https://github.com/pixiebrix/pixiebrix-extension/blob/18f70097df95d11d784636d7b4a8b84750c15258/end-to-end-tests/pageObjects/pageEditor/pageEditorPage.ts#L166