Optimize model picker search rerenders

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What Changed

• Split the model picker search input into a small memoized component that owns the raw input text.
• Keep ModelPickerContent subscribed only to the normalized search query, so whitespace-only edits do not invalidate the picker/list tree.
• Preserved Escape and Enter behavior by passing stable callbacks into the search input.

Why

React Doctor highlighted a broader React performance backlog, and a manual React Scan pass found a measurable model-picker hotspot: typing whitespace in the model search box changed no visible rows but still rerendered the picker content and row area. This change keeps behavior predictable while avoiding those no-op parent/list renders.

UI Changes

No visual UI change. React Scan recordings captured with the temporary harness and toolbar enabled:

• Before: react_scan_model_picker_before.mp4 — whitespace typing triggered React Scan highlights/rerenders in the picker path.
• After: react_scan_model_picker_after.mp4 — the same whitespace typing produced no picker/list rerender highlights; counts stayed at ModelPickerContent: 2, ModelListRow: 19.

Checklist

• This PR is small and focused
• I explained what changed and why
• I included before/after screenshots for any UI changes
• I included a video for animation/interaction changes

Validation:

• react-doctor --verbose -y --offline --category performance --blocking none
• vp check
• vp run typecheck

  

Note

Reduce rerenders in model picker search by memoizing the search input component

• Extracts the search input into a memoized ModelPickerSearchInput component in ModelPickerContent.tsx to prevent unnecessary rerenders.
• Trims whitespace from search queries via normalizeModelSearchQuery and skips calling onSearchQueryChange when the normalized value is unchanged.
• Memoizes the submitHighlightedModel callback and wires Enter key submission through the new child component.

^{Macroscope summarized 6d9e4a1.}