fix(plugin-detail): reveal the read-only field's copy button on keyboard focus

Claude-Session: https://claude.ai/code/session_01SMps7wq7rBTk53e8KTSEup
Co-authored-by: Claude <noreply@anthropic.com>

Author: claude

.changeset/26329-copy-button-focus-reveal.md

@@ -0,0 +1,12 @@
+---
+'@object-ui/plugin-detail': patch
+---
+
+fix(plugin-detail): reveal the read-only field's copy button on keyboard focus
+
+Clause-②: no
+Metadata-protocol: none
+
+On a record page in desktop read mode, the copy-to-clipboard button beside a read-only, copyable field was shown on hover only. It is a real button, so a keyboard user's Tab stop landed on a control they could not see. It is now also shown while it has keyboard focus, or while anything else in its field has focus (for example the field's own click-to-copy row), in the same way as the inline-edit pencil beside it. Hover, click-to-copy and the button's accessible name are unchanged.
+
+What to do: nothing.

ui/packages/plugin-detail/src/DetailSection.tsx

@@ -772,7 +772,9 @@ export const DetailSection: React.FC<DetailSectionProps> = ({
                   <Button
                     variant="ghost"
                     size="icon"
-                    className="h-6 w-6 opacity-0 group-hover:opacity-100 transition-opacity shrink-0"
+                    // A real Tab stop, so it is revealed on keyboard focus as
+                    // well as on hover, like the pencil above (objectstack#26329).
+                    className="h-6 w-6 opacity-0 group-hover:opacity-100 group-focus-within:opacity-100 focus-visible:opacity-100 transition-opacity shrink-0"
                     // objectui#12625 — an icon-only button; the tooltip is
                     // closed at rest, so without this it has no name.
                     aria-label={t('detail.copyToClipboard')}