fix(capture): lower inventory PNG floor to 800px

Product call for the WooCommerce redo. Calculate accepts
sources whose post-crop shorter side is at least 800px.
Warn copy and CAPTURE.md match. No upscale still holds.

docs/CAPTURE.md

@@ -109,7 +109,7 @@ On Calculate, the app builds the inventory image from the approved mask:
 1. Keep slab pixels from the source photo. Removed pixels are transparent.
 2. Place the slab in a 3:4 portrait frame, centered.
 3. Scale so the widest and tallest points of the slab fill 80% of the frame. Extra margin where the slab is narrower.
-4. After that crop, shorter side ≥ 1600px when the source can supply it. Otherwise warn and require a new photo. No upscale from an undersized source.
+4. After that crop, shorter side ≥ 800px when the source can supply it. Otherwise warn and require a new photo. No upscale from an undersized source.
 5. Encode as PNG with alpha.
 
 ## Device draft
@@ -134,7 +134,7 @@ The first inventory photo is the measurement reference. Later inventory photos u
 | Alpha | Kept through encode and upload |
 | Aspect | 3:4 portrait |
 | Layout | Slab centered, 80% fill at the widest and tallest points |
-| Size | After crop, shorter side ≥ 1600px when the source can supply it |
+| Size | After crop, shorter side ≥ 800px when the source can supply it |
 
 Source below that floor: warn and require a new photo. No upscale from an undersized source.
 Editor preview of alpha is a light gray checkerboard. The storefront uses the theme background.

frontend/src/capture/MeasurePanel.svelte

@@ -107,7 +107,7 @@
         <div><span>Scale</span><span>{state.results.scale.toFixed(2)} px/in</span></div>
       </div>
       {#if state.results.sourceBelowFloor}
-        <div class="warn">Source is below the 1600px floor for the inventory PNG. Retake a larger photo.</div>
+        <div class="warn">Source is below the 800px floor for the inventory PNG. Retake a larger photo.</div>
       {/if}
       {#if pngUrl && !state.results.sourceBelowFloor}
         <div class="png-wrap">

frontend/src/png/inventory.test.ts

@@ -31,7 +31,7 @@ test('alpha contract: removed pixels transparent, slab pixels keep RGB at alpha
   const out = composeInventoryFrame(src, maskFor(bitset, { x: 1, y: 1, w: 4, h: 4 }), source);
 
   assert.equal(out.sourceBelowFloor, true);
-  assert.ok(out.width < 1600, 'undersized source stays small');
+  assert.ok(out.width < 800, 'undersized source stays small');
 
   let opaque = 0;
   let transparent = 0;
@@ -56,7 +56,7 @@ test('alpha contract: removed pixels transparent, slab pixels keep RGB at alpha
   assert.ok(transparent > 0, 'frame has transparent pixels');
 });
 
-test('3:4 frame at the floor: 2000×1800 slab → 1600×2133', () => {
+test('3:4 frame at the floor: 2000×1800 slab → 800×1067', () => {
   const source: Pick<Source, 'widthPx' | 'heightPx'> = { widthPx: 2000, heightPx: 1800 };
   const bitset = new Uint8Array(source.widthPx * source.heightPx).fill(1);
   const out = composeInventoryFrame(
@@ -64,11 +64,23 @@ test('3:4 frame at the floor: 2000×1800 slab → 1600×2133', () => {
     maskFor(bitset, { x: 0, y: 0, w: 2000, h: 1800 }),
     source,
   );
-  assert.equal(out.width, 1600);
-  assert.equal(out.height, 2133);
+  assert.equal(out.width, 800);
+  assert.equal(out.height, 1067);
   assert.equal(out.sourceBelowFloor, false);
 });
 
+test('mid-band: slab shorter side 1000 (between 800 and 1600) → at floor, not belowFloor', () => {
+  const source: Pick<Source, 'widthPx' | 'heightPx'> = { widthPx: 1200, heightPx: 1000 };
+  const bitset = new Uint8Array(source.widthPx * source.heightPx).fill(1);
+  const out = composeInventoryFrame(
+    makePhoto(source.widthPx, source.heightPx),
+    maskFor(bitset, { x: 0, y: 0, w: 1200, h: 1000 }),
+    source,
+  );
+  assert.equal(out.sourceBelowFloor, false);
+  assert.equal(out.width, 800);
+});
+
 test('80% fill: limiting dimension maps to 0.8 × frame side', () => {
   const source: Pick<Source, 'widthPx' | 'heightPx'> = { widthPx: 2200, heightPx: 2000 };
   const bitset = new Uint8Array(source.widthPx * source.heightPx).fill(1);
@@ -91,11 +103,11 @@ test('80% fill: limiting dimension maps to 0.8 × frame side', () => {
   const xs = [minx, maxx], ys = [miny, maxy];
   const wExtent = Math.max(...xs) - Math.min(...xs) + 1;
   const hExtent = Math.max(...ys) - Math.min(...ys) + 1;
-  assert.ok(Math.abs(wExtent - 1280) <= 2, `width extent ${wExtent} ≈ 1280 (0.8×1600)`);
-  assert.ok(Math.abs(hExtent - 1152) <= 2, `height extent ${hExtent} ≈ 1152 (0.8×1800×0.64)`);
+  assert.ok(Math.abs(wExtent - 640) <= 2, `width extent ${wExtent} ≈ 640 (0.8×800)`);
+  assert.ok(Math.abs(hExtent - 576) <= 2, `height extent ${hExtent} ≈ 576 (1800×0.32)`);
 });
 
-test('belowFloor: small slab → sourceBelowFloor, outW < 1600', () => {
+test('belowFloor: small slab → sourceBelowFloor, outW capped at floor (no upscale)', () => {
   const source: Pick<Source, 'widthPx' | 'heightPx'> = { widthPx: 900, heightPx: 700 };
   const bitset = new Uint8Array(source.widthPx * source.heightPx).fill(1);
   const out = composeInventoryFrame(
@@ -104,5 +116,5 @@ test('belowFloor: small slab → sourceBelowFloor, outW < 1600', () => {
     source,
   );
   assert.equal(out.sourceBelowFloor, true);
-  assert.ok(out.width < 1600, `outW ${out.width}`);
+  assert.ok(out.width <= 800, `outW ${out.width} must not exceed the floor`);
 });

frontend/src/png/inventory.ts

@@ -1,6 +1,6 @@
 import type { Mask, Source } from '../capture/capture.types';
 
-const FLOOR = 1600; // shorter side, px
+const FLOOR = 800; // shorter side, px
 const FILL = 0.8; // 80% fill at the widest and tallest points of the slab
 const ASPECT_W = 3;
 const ASPECT_H = 4;