fix(editor): guard unresolved page mentions and bare anchor links

A page mention without a slug rendered as a link ending in -null; it now
renders as plain text. A link whose href is a bare #fragment scrolls to
the target on the current page instead of opening about:blank.

apps/client/src/features/editor/components/link/link-view.tsx

@@ -224,6 +224,16 @@ export default function LinkView(props: MarkViewProps) {
   const handleNavigate = useCallback(() => {
     if (!href) return;
 
+    if (href.startsWith("#")) {
+      const anchor = href.slice(1);
+      const element =
+        document.querySelector(`[id="${anchor}"]`) ||
+        document.querySelector(`[data-id="${anchor}"]`);
+      element?.scrollIntoView({ behavior: "smooth", block: "start" });
+      navigate(`${location.pathname}#${anchor}`, { replace: true });
+      return;
+    }
+
     if (isInternal) {
       let targetPath = href;
       let anchor = "";

apps/client/src/features/editor/components/mention/mention-view.tsx

@@ -15,6 +15,7 @@ export default function MentionView(props: NodeViewProps) {
   const { node } = props;
   const { label, entityType, entityId, slugId, anchorId } = node.attrs;
   const isPageMention = entityType === "page";
+  const hasTarget = isPageMention && !!slugId;
   const { spaceSlug, pageSlug } = useParams();
   const { shareId } = useParams();
   const navigate = useNavigate();
@@ -63,7 +64,22 @@ export default function MentionView(props: NodeViewProps) {
         </Text>
       )}
 
-      {isPageMention && isShareRoute && (
+      {isPageMention && !hasTarget && (
+        <Text component="span" fw={500} className={classes.pageMentionLink}>
+          <ActionIcon
+            variant="transparent"
+            color="gray"
+            component="span"
+            size={18}
+            style={{ verticalAlign: "text-bottom" }}
+          >
+            <IconFileDescription size={18} />
+          </ActionIcon>
+          <span className={classes.pageMentionText}>{label}</span>
+        </Text>
+      )}
+
+      {hasTarget && isShareRoute && (
         <Anchor
           component={Link}
           fw={500}
@@ -87,7 +103,7 @@ export default function MentionView(props: NodeViewProps) {
         </Anchor>
       )}
 
-      {isPageMention && !isShareRoute && isError && (
+      {hasTarget && !isShareRoute && isError && (
         <Anchor
           component={Link}
           fw={500}
@@ -111,7 +127,7 @@ export default function MentionView(props: NodeViewProps) {
         </Anchor>
       )}
 
-      {isPageMention && !isShareRoute && !isError && (
+      {hasTarget && !isShareRoute && !isError && (
         <Anchor
           component={Link}
           fw={500}