feat(client): improve accessibility with ARIA labels and semantics

- Add aria-label to icon-only ActionIcon triggers across tree, comments,
  share, group, breadcrumbs, templates, AI chat, API keys, and spaces
- Give custom clickable divs/spans (color swatches, status swatches,
  load-more, PDF error, comment selection) role="button", tabIndex,
  and keyboard handlers
- Add listbox/combobox semantics (role, aria-selected, aria-activedescendant)
  to slash menu, emoji menu, mention list, and link editor results
- Add aria-haspopup/aria-expanded to bubble-menu triggers (node, text
  align, color) and status badge
- Add aria-label to Modal.Root/Dialog instances that lack a title prop
  (page history, template preview, trash preview, drawio, comment,
  find-and-replace, page verification)
- Add en-US translations for new aria-label strings

apps/client/src/components/common/copy.tsx

@@ -25,6 +25,7 @@ export default function CopyTextButton({ text, size }: CopyProps) {
             variant="subtle"
             onClick={copy}
             size={size}
+            aria-label={copied ? t("Copied") : t("Copy")}
           >
             {copied ? <IconCheck size={16} /> : <IconCopy size={16} />}
           </ActionIcon>

apps/client/src/components/ui/destination-picker/page-children.tsx

@@ -74,7 +74,18 @@ export function PageChildren({
         />
       ))}
       {hasNextPage && (
-        <div className={classes.loadMore} onClick={() => fetchNextPage()}>
+        <div
+          className={classes.loadMore}
+          onClick={() => fetchNextPage()}
+          onKeyDown={(e) => {
+            if (e.key === "Enter" || e.key === " ") {
+              e.preventDefault();
+              fetchNextPage();
+            }
+          }}
+          role="button"
+          tabIndex={0}
+        >
           {t("Load more")}
         </div>
       )}

apps/client/src/components/ui/emoji-picker.tsx

@@ -70,11 +70,14 @@ function EmojiPicker({
       closeOnEscape={true}
     >
       <Popover.Target ref={setTarget}>
-        <ActionIcon 
-          c={actionIconProps?.c || "gray"} 
-          variant={actionIconProps?.variant || "transparent"} 
+        <ActionIcon
+          c={actionIconProps?.c || "gray"}
+          variant={actionIconProps?.variant || "transparent"}
           size={actionIconProps?.size}
           onClick={handlers.toggle}
+          aria-label={t("Pick emoji")}
+          aria-haspopup="dialog"
+          aria-expanded={opened}
         >
           {icon}
         </ActionIcon>