unify boxed conversation-card interior padding (T-282)

Bordered cards (tool / Agent calls) used 10px vertical interior padding while
stripe cards (you / claude) used 8, so a collapsed tool/Agent card read
chunkier — taller box and more trailing space — than its neighbours in the
conversation log. Match the bordered variant's vertical padding to the stripe
variant (8) so boxed cards share one rhythm. Box-to-box inter-card margin is
unchanged (a uniform 14). Regenerated the merged-card golden.

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

lib/builtin/claude/src/conversation_card.dart

@@ -216,7 +216,10 @@ class _ConversationCardState extends State<ConversationCard> {
         );
       case ConversationCardVariant.bordered:
         return Container(
-          padding: const EdgeInsets.all(10),
+          // Vertical interior padding matches the stripe variant (8) so boxed
+          // cards share one rhythm — a collapsed tool/Agent card no longer reads
+          // chunkier (taller box + more trailing space) than its neighbours (T-282).
+          padding: const EdgeInsets.fromLTRB(10, 8, 10, 8),
           decoration: BoxDecoration(
             color: tokens.globalBackground,
             border: Border.all(color: widget.borderColor ?? tokens.panelBorder),