[o1y]

Fixes #15659

When you type fast in a Bard inside another Bard set, the last few characters can vanish (a short pause is enough). The same problem is for List and Array fields inside a Bard set.

Fields inside a set write straight into the container. About 150 ms later the outer Bard emits the whole field again, so the nested Bard gets a copy of a value it already had. Its own update is still debounced, so it sees a mismatch and rebuilds, losing the newer typing.

Solution

• Bard doesn't emit when the container already has the value. The value rebuild from the value watcher now clones the value (like initEditor does).
• Bard ignores a value identical to the previous one (the same guard which is also there for Tables).

Unlike #15702, where the outer Bard sent back an outdated copy of the set values, the copy here is up to date. But the nested Bard has already moved past it, because its own update is still debounced so it throws away the newer typing.