M3.1 follow-up: ShareCard grade-B billboard → Design white; drop stale comment hexes

The share/OG card (a billboard) still painted grade B blue (#4A9EFF) on canvas;
Design's B is neutral-bright white. Canvas needs a literal, so #F0F0F0 direct.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web/src/app/globals.css

@@ -37,7 +37,7 @@
      — aligned to Design 2026-07-16. Amber stays its own token (--amber). */
   --grade-aplus: #00FFB8;
   --grade-a:     #00D4A0;
-  --grade-b:     #F0F0F0;   /* was #4A9EFF (blue) */
+  --grade-b:     #F0F0F0;   /* neutral-bright white (was blue) */
   --grade-c:     #B8BCC8;   /* was #FFB347 (amber) */
   --grade-d:     #FF4757;   /* was #FF5252 */
 
@@ -78,7 +78,7 @@
   /* Grade tokens (the product's core color language) */
   --g-ap: #00ffb8;   /* A+  rarest, max glow */
   --g-a:  #00d4a0;   /* A   workhorse green / primary CTA */
-  --g-b:  #F0F0F0;   /* B   neutral-bright white (Design; was blue) */
+  --g-b:  #F0F0F0;   /* B   neutral-bright white (Design) */
   --g-c:  #B8BCC8;   /* C   muted grey (Design; was amber) */
   --g-d:  #FF4757;   /* D   red (Design; was #ff5252) */
 

web/src/components/ShareCard.tsx

@@ -23,7 +23,7 @@ const SPORT_COLOR: Record<ShareCardProps['sport'], string> = {
 function gradeColor(grade: string): string {
   const g = (grade || '').trim().toUpperCase().charAt(0);
   if (g === 'A') return '#00C896';
-  if (g === 'B') return '#4A9EFF';
+  if (g === 'B') return '#F0F0F0';
   if (g === 'C') return '#FFB347';
   return '#FF6B6B';
 }