Restore width-fit ratio bands for native FOV plain preview

Plain frame 'none' with ratio 4:3 shows the whole sensor at screen width (85 deg FOV, like the built-in app at 23mm equiv); 3:2 crops the two vertical sides, same height and zoom, matching the export crop. The fullscreen-cover plain preview from 7985f25 was a wrong interpretation of the built-in view and made every ratio look identical fullscreen.

src/components/Viewfinder.tsx

@@ -115,23 +115,14 @@ export default function Viewfinder({
 
   // Composition ratio band. With a ratio active the photo area is a centered
   // portrait strip (w/h = ratioWH) and everything outside is letterboxed;
-  // exports crop to the same ratio. The border/bars frames (classic-white,
-  // cinematic) use the band because their geometry must hug the photo edges;
-  // polaroid keeps its own card layout (window aspect follows the ratio) and
-  // the wall frame deliberately ignores the ratio entirely (fixed 2:3 window).
-  // A PLAIN preview (frame 'none') with a ratio does NOT band in camera mode:
-  // it stays the fullscreen cover view of FULL/1x so the angle of view matches
-  // the built-in camera app at 1x — contain-fitting the whole sensor into a
-  // strip reads as a crop next to the native app's zoomed fullscreen preview
-  // (export still crops to the ratio). When no band is active the region is
-  // just the full screen, so every consumer below degrades to the old
-  // fullscreen behavior untouched.
+  // exports crop to the same ratio. Only the plain full-picture frames use the
+  // band — polaroid keeps its own card layout (window aspect follows the ratio)
+  // and wall frame deliberately ignores the ratio entirely (its opening is a
+  // fixed 2:3). When no band is active the region is just the full screen, so
+  // every consumer below degrades to the old fullscreen behavior untouched.
   const ratioWH = aspectRatio === 'full' ? null : ASPECT_RATIO_W_H[aspectRatio];
-  const plainRatio =
-    mode === 'camera' && selectedFrame === 'none' && ratioWH !== null;
   const regionBand =
     ratioWH !== null &&
-    !plainRatio &&
     (selectedFrame === 'none' || selectedFrame === 'classic-white' || selectedFrame === 'cinematic');
   const region = useMemo(() => {
     if (!regionBand || ratioWH === null) return { x: 0, y: 0, w: vw, h: vh };
@@ -591,12 +582,10 @@ export default function Viewfinder({
     return wallframeLayout(vw, vh, 'contain');
   }, [selectedFrame, vw, vh]);
   // Live feed band rect for the CAMERA preview: the photo-area that must show
-  // the export-equivalent sensor crop — the ratio band region (classic-white /
-  // cinematic frames), the polaroid photo window or the wall-frame window.
-  // When present the frame worklet redraws the feed into it (native 4:3 shows
-  // the whole sensor); when null ([0]=0) the feed stays the legacy fullscreen
-  // cover draw — that is also the plain 'none' + ratio case now, which shows
-  // the built-in-camera 1x view instead of a banded whole-sensor strip.
+  // the export-equivalent sensor crop — the ratio band region (plain frames),
+  // the polaroid photo window or the wall-frame window. When present the frame
+  // worklet redraws the feed into it (native 4:3 shows the whole sensor);
+  // when null ([0]=0) the feed stays the legacy fullscreen cover draw.
   const cameraPhotoRect =
     mode === 'camera'
       ? polaroidGeo
@@ -856,9 +845,7 @@ export default function Viewfinder({
       <Canvas style={StyleSheet.absoluteFill} pointerEvents="none">
         {/* Aspect-ratio band: black out the live feed outside the composition
             region. Frames with their own geometry (polaroid/wall) draw their
-            own bars later; the plain 'none' camera preview no longer bands
-            (fullscreen 1x view), so this only fires for classic-white and
-            cinematic, whose border/bars must sit on the photo edges. */}
+            own bars later, so this only fires for the plain frames. */}
         {regionBand && (
           <Group color="#000000">
             <Rect x={0} y={0} width={vw} height={region.y} />