There was no zoom/pan reset on main to fix: what this PR changes is that a
zoomed view with the mask overlay shown is now a canvas-sized frame plus a
sharp window carrying the overlay, as without it, instead of a whole-frame
render at the zoomed size. Tests: the overlay on a window matches the same
pixels of the whole render for radial, refined linear and sky masks in
three views (pipeline tests_window.rs), and at 1:1 the loupe uses a window
with the overlay, keeps zoom and pan, and swaps tiles when the overlay is
hidden or shown (ui-egui tests_preview_limit.rs). Parity row updated. No
render output change (no cache bump).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
