chore(ui): tighten and center bulk delete toolbar

packages/ui/src/styles/messaging/message-selection.css

@@ -11,20 +11,29 @@
 
 .message-delete-mode-toolbar {
   position: absolute;
-  right: 5rem;
+  left: 50%;
+  transform: translateX(-50%);
   bottom: 1rem;
-  display: flex;
-  flex-wrap: wrap;
+  display: inline-flex;
+  flex-direction: column;
   align-items: center;
   gap: 6px;
   padding: 6px 10px;
-  background: color-mix(in oklab, var(--surface-base) 62%, var(--accent-primary));
-  border: 1px solid var(--accent-primary);
+  /* Match other popups (dropdown-surface / panels) */
+  background-color: var(--surface-base);
+  border: 1px solid var(--border-base);
   border-radius: 12px;
   z-index: 50;
-  box-shadow:
-    0 0 0 1px color-mix(in oklab, var(--accent-primary) 25%, transparent),
-    0 8px 24px rgba(0, 0, 0, 0.3);
+  box-shadow: var(--panel-shadow-strong);
+  width: max-content;
+  max-width: min(80vw, 560px);
+}
+
+.message-delete-mode-toolbar-row {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  gap: 6px;
 }
 
 .message-delete-mode-token-group {
@@ -202,7 +211,6 @@
 }
 
 .message-delete-mode-hint-row {
-  flex: 1 0 100%;
   display: flex;
   align-items: center;
   justify-content: center;
@@ -211,10 +219,11 @@
   font-size: 10px;
   color: var(--text-muted);
   user-select: none;
+  flex-wrap: wrap;
 }
 
 .message-delete-mode-hint-text {
-  white-space: nowrap;
+  white-space: normal;
 }
 
 .message-delete-mode-hint-sep {