fix(html-embed): address code-review findings on the sandbox commit

Follow-up fixes to the htmlEmbed-sandbox / trackerHead change:

- share-seo: inject trackerHead via a function replacer so `$`-sequences
  ($&, $', $`, $$) in the admin snippet are inserted literally instead of
  being treated as String.replace substitution patterns; warn when the
  </head> marker is absent instead of silently skipping injection.
- mcp: register a passthrough `htmlEmbed` node in the schema mirror so an
  AI/MCP edit of a page containing an embed no longer throws
  "Unknown node type: htmlEmbed" in TiptapTransformer.toYdoc.
- editor-ext + client: treat a non-finite `data-height` as auto (null) so a
  crafted/corrupted height cannot disable auto-resize or yield a NaN iframe
  height; extract a shared clampHeight helper.
- client: rename render-raw-html.{ts,test.ts} -> html-embed-sandbox.{...} and
  shouldExecute -> shouldRender so the seam name matches the sandbox model.
- client: i18n the iframe title; surface the real error reason in
  tracker-settings (console.error + err.response.data.message).
- docs: note hasHtmlEmbedNode is now a test-only helper; add an Unreleased
  CHANGELOG entry; drop the dangling "arbitrary HTML embed" planning-doc ref.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

apps/client/src/features/workspace/components/settings/components/tracker-settings.tsx

@@ -46,9 +46,10 @@ export default function TrackerSettings() {
       });
       notifications.show({ message: t("Updated successfully") });
     } catch (err) {
-      console.log(err);
+      console.error("Failed to update tracker settings", err);
       notifications.show({
-        message: t("Failed to update data"),
+        message:
+          (err as any)?.response?.data?.message ?? t("Failed to update data"),
         color: "red",
       });
     } finally {