Expand the search field while filtering

[alvst]

What changed

• Expands the search field with a spring animation while typing.
• Caps its expanded width at 700 points and preserves navigation space on narrower windows.
• Keeps the newest portion of a long query visible and collapses the control when it is cleared.

Why

The compact search pill makes longer queries difficult to inspect and edit.

Validation

• swift build
• git diff --check

Screenshots

Demo mode — Pesty window only.