chore: memoize tabs children

[lawreka]

Summary

luckily we don't have the useTabsState hook here that we do in client for syncing + doing weird navigation jumps around when versions/dropdowns change, so this is a very light improvement

Test Plan

• no visual changes

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Note

Low Risk
Simple useMemo optimization in a UI component; low chance of behavioral impact beyond subtle changes if callers pass unstable children references.

Overview
Reduces unnecessary recomputation in TabsRoot by memoizing the derived arrayChildren list and the generated tabIds via useMemo, keeping IDs stable across renders unless children (or the component’s useId) changes.

No behavior or API surface is intentionally changed; this is a render/performance optimization for consumers like code-group and other Tabs usages.

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