The salvaged measurement effect only listened to window `resize`, so
opening, closing, or drag-resizing the files pane while the find bar was
up left the bar in a stale position (either still covering the pane's
header or floating mid-window after the pane closed).
Harden the measurement path:
- ResizeObserver on the aside tracks drag-resizes of the pane rail.
- A body-scoped childList MutationObserver catches the pane mounting or
unmounting mid-find-session and retargets the ResizeObserver when the
aside's identity changes (pane reopened, panes flipped).
- All triggers coalesce into a single rAF-batched measure; everything
(observers, listener, pending frame) tears down when the bar closes.
Also extends find-bar.test.tsx with three positioning tests: default
right-4 when the pane is closed, parked left of an open pane, and
re-measuring when the pane opens/closes while the bar is up.
Teknium
d8536709b7