round 4: app-shell quiz screen at <=700px — #step-body is the only scroller, #btn-next/#panel become the static bottom cluster; revert FR .opt override (keep 972f3a7); + capture/verify/pixdiff/offlan audit tooling and before/after evidence; closes QUIZ-APPSHELL-FIX.md

audit/appshell_pixdiff.py

@@ -0,0 +1,40 @@
+"""Pixel-diff two screenshot dirs (matching filenames). Usage:
+python3 audit/appshell_pixdiff.py DIR_A DIR_B [label_a label_b]
+Prints per-file diff pixel counts + max channel delta; PIXDIFF-ZERO if every shared
+file matches bit-for-bit. Also flags size mismatches."""
+import os, sys
+from PIL import Image, ImageChops
+
+A, B = sys.argv[1], sys.argv[2]
+la, lb = (sys.argv[3:5] or ['A', 'B'])
+fa = sorted(f for f in os.listdir(A) if f.endswith('.png'))
+fb = sorted(f for f in os.listdir(B) if f.endswith('.png'))
+missing = set(fa) - set(fb)
+if missing:
+    print('FILES MISSING IN', lb, ':', sorted(missing))
+zero, n = True, 0
+for f in fa:
+    if f not in fb:
+        continue
+    n += 1
+    ia, ib = Image.open(os.path.join(A, f)), Image.open(os.path.join(B, f))
+    if ia.size != ib.size:
+        print(f'{f}: SIZE DIFF {ia.size} vs {ib.size}')
+        zero = False
+        continue
+    d = ImageChops.difference(ia.convert('RGB'), ib.convert('RGB'))
+    bbox = d.getbbox()
+    if bbox is None:
+        print(f'{f}: 0 px diff (identical)')
+    else:
+        hist = d.convert('L').histogram()
+        ndiff = sum(hist[1:])
+        mx = max(i for i, c in enumerate(hist) if c)
+        pct = ndiff / (ia.size[0] * ia.size[1]) * 100
+        print(f'{f}: {ndiff} px diff ({pct:.4f}%), bbox {bbox}, maxdelta {mx}')
+        zero = False
+if n == 0:
+    print('no shared files!')
+    zero = False
+print('PIXTDIFF-ZERO' if zero else 'PIXTDIFF-NONZERO')
+sys.exit(0 if zero else 1)