GPU art: drop the diagonal stub at the end of the accent stripe; appraisal test helpers

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

art/sprites.py

@@ -186,8 +186,6 @@ def gpu_front(accent, accent_dark, burnt=False):
     for y in range(TOP0 + 3, TOP1 - 2):
         c.put(25, y, 'k'); c.put(26, y, 'x')
     # 品牌色斜条（从前沿向左上延伸）与前沿色条
-    for k in range(0, 8):
-        c.put(L + 3 + k, TOP1 - 1 - k // 2, accent)
     for x in range(L + 1, R - 5):
         c.put(x, TOP1 - 1, accent if x % 9 else accent_dark)
         c.put(x, TOP1, accent_dark)
@@ -255,8 +253,6 @@ def gpu_back(accent, accent_dark, burnt=False):
     for x in range(L + 1, R - 1):
         c.put(x, 16, accent)
     c.put(L + 1, 17, accent_dark); c.put(R - 2, 17, accent_dark)
-    for k in range(0, 7):
-        c.put(R - 3 - k, 15 - k // 2 if k < 4 else 14, accent_dark)
     # 通风槽（左下一组）
     for y in (19, 21, 23, 25):
         for x in range(L + 4, L + 14):