match folded activity-card spacing to the conversation cards (T-282)

The collapsed activity / agent-run cards (ClideHolderCard) wrapped themselves
in 3px vertical margin, while the prose ConversationCards use 14px bottom /
0 top. So a folded card floated ~17px below the previous card but hugged the
next one at 3px — the uneven gap the earlier bordered-padding tweak didn't
address. Give the holder the same bottom-14 / top-0 margin.

The holder-card golden is regenerated for the taller frame. The copy-button
holder test parks its hover and advances past the tooltip show-delay so the
(exit-uncancellable) Future.delayed timer fires instead of leaking.

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

lib/builtin/claude/src/holder_card.dart

@@ -72,7 +72,10 @@ class _ClideHolderCardState extends State<ClideHolderCard> {
       label: '${widget.title}, ${widget.stepLabel}, ${_expanded ? 'expanded' : 'collapsed'}',
       excludeSemantics: true,
       child: Padding(
-        padding: const EdgeInsets.symmetric(vertical: 3),
+        // Match ConversationCard's inter-card margin (bottom 14, no top) so a
+        // folded activity / agent-run card sits in the same rhythm as the prose
+        // cards around it — not crammed 3px below the next one (T-282).
+        padding: const EdgeInsets.only(bottom: 14),
         child: _expanded ? _expandedFrame(tokens) : _tickerRow(tokens),
       ),
     );