fix(ui): prevent crash when deleting ReplicaSet from grouped list

[choejwoo]

Closes #26066

I reproduced the issue locally. I was able to reproduce the problem (see the attached screenshot).

The root cause was that deleting an old ReplicaSet from the grouped resources list could crash the UI with TypeError: Cannot read properties of undefined (reading 'info'), so I added a guard to avoid dereferencing a missing tree node and confirmed the crash no longer occurs.

After that, I also fixed a UX issue where the grouped resources panel kept a stale snapshot, causing deleted ReplicaSets to remain visible until the drawer was reopened, the panel now stores selected grouped IDs and derives the list from the latest tree/app state, and Delete triggers an immediate refresh via appChanged. As a result, the UI no longer crashes and the grouped list updates immediately after deletion (see the attached video).

2026-01-28.8.06.32.mov

Checklist:

• Either (a) I've created an enhancement proposal and discussed it with the community, (b) this is a bug fix, or (c) this does not need to be in the release notes.
• The title of the PR states what changed and the related issues number (used for the release note).
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