[6.x] Fix CP tab crash when expanding a Bard set after a copy

[o1y]

Fixes #14946

The chromium render crash ("Aw, Snap") fires when all of these line up in the same click

1. A rich copy is on the clipboard (text copied from inside a Bard editor).
2. A hidden Bard editor is revealed (the set's content goes from display:none to visible).
3. The set's content animates as it appears (the header transition + the fields fading in). This was not there in V5, so this is why this bug was probably not triggering there.

When all three happen inside the one click, Chrome probably trips over its own editing/clipboard code and kills the tab.

In this commit we defer the reveal by one animation frame so the Bard editor is shown just after the click. That moves the work off the click, and the crash can't happen.

[o1y]

Whoa. I'm converting this PR to a draft, as I've realized that quite a few fields are affected by this bug and proper testing is needed here. Maybe the team can take it from here. Unfortunately, we're also hitting this crash a few times a day and losing content.. I was hoping it'd be an easy fix 😅

Other reveal-on-click surfaces (collapsible sections, tabs, revealer) share the same pattern and likely need the same guard as well (not verified though)..

[jasonvarga]

I've thrown my buddy Claude at it. I'll either update this PR or open up a new one.

[o1y]

Well then let Claude decide! 🥲

[macaws]

@jasonvarga what was the outcome of that? We're now affected by this bug so anything we can do to help :)

[jasonvarga]

I've opened #14967 blindly. I couldn't reproduce the bug myself. Would one or either of you be able to test that PR to see if it fixes the issue? We can continue the conversation there.