Wrap transcript card actions under the title on narrow screens

Polish pass on the translate panel: the four export buttons overflowed
both transcript cards at 390 px. Also record the headless-Chrome
translation run and a re-measured bench in D-WS4b.

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

src/index.css

@@ -773,7 +773,8 @@ body {
   display: flex;
   align-items: center;
   justify-content: space-between;
-  gap: 1rem;
+  flex-wrap: wrap;
+  gap: 0.5rem 1rem;
 }
 
 .transcript-header h2 {
@@ -1004,6 +1005,7 @@ code {
 .transcript-actions {
   display: flex;
   align-items: center;
+  flex-wrap: wrap;
   gap: 0.5rem;
 }
 
@@ -1062,7 +1064,7 @@ code {
   font-size: 0.85rem;
   cursor: pointer;
   white-space: nowrap;
-  transition: border-color 0.15s, color 0.15s;
+  transition: border-color 0.15s, color 0.15s, background-color 0.15s;
 }
 
 /* The panel's one action reads as the action: accent outline, like a