Command Palette: Search result scroll jumps and layout jitters

[DarkMatter-999]

What?

Closes #77021

This is a solution for current Command Palette, before when we move away from cmdk, as mentioned here.

Why?

This PR fixes a UI isssue in the Command Palette where the results list would unexpectedly scroll downward or "jitter" when filtering results.

The issue was caused by a conflict between cmdk’s internal scroll-into-view logic and the asynchronous nature of command loaders. When new results were injected or the search string changed, the library would attempt to center the active selection. If this happened while the DOM was still reconciling or the list height was shifting, it resulted in a "jump" that disoriented the user.

How?

To ensure a stable and "sticky" scroll position at the top of the list during filtering, added a useLayoutEffect hook in CommandMenu that targets the [cmdk-list] container. It synchronously resets scrollTop to 0 whenever the search state or loadersLoading state changes.

Because cmdk occasionally triggers its own scroll logic asynchronously (after the initial render), the reset logic uses an animation loop. This "guards" the scroll position for 10 frames (~160ms) to override any late-firing internal library scrolls.

Testing Instructions

1. Open the Command Palette (e.g., via Cmd+K)
2. Type "t", the results updates, with selected result un the top.
3. Type "a", so the search term becomes "ta", the search results stay in the view.
4. Complete typing the whole search term, "tags."

Screenshots or screencast

Before

command-palette.mp4

After

command-palette-fix.mp4

Use of AI Tools

Gemini 3.1 Pro and Claude Sonnet 4.6 were used for research.

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