fix(session-ui): align code copy tooltip with v2 style (#34459)

Co-authored-by: Jay <53023+jayair@users.noreply.github.com>
Co-authored-by: opencode-agent[bot] <opencode-agent[bot]@users.noreply.github.com>

packages/session-ui/src/components/markdown.css

@@ -327,6 +327,29 @@
   }
 }
 
+body[data-new-layout] [data-component="markdown"] {
+  [data-slot="markdown-copy-button"]::after {
+    box-sizing: border-box;
+    display: inline-flex;
+    flex-direction: row;
+    align-items: center;
+    gap: 6px;
+    padding: 5px 6px;
+    border: 0;
+    border-radius: 4px;
+    background: var(--v2-background-bg-layer-01);
+    box-shadow: var(--v2-elevation-floating);
+    color: var(--v2-text-text-base);
+    user-select: none;
+    font-size: 11px;
+    font-weight: 530;
+    line-height: 12px;
+    letter-spacing: 0.05px;
+    font-variant-numeric: tabular-nums;
+    font-variation-settings: "slnt" 0;
+  }
+}
+
 body:not([data-new-layout]) [data-component="markdown"] {
   color: var(--text-strong);