fix(navigation): support anchor fragments in note links

Links like `path/to/note.md#heading` previously errored with "Note not
found" because the full href (including `#hash`) was matched against
file paths. Split the fragment off in the link handler, plumb it through
the event bus, and scroll the matching heading into view once the
target note is in place. Headings now get GitHub-style ids via
markdown-it-anchor + github-slugger so the anchors actually exist.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/hooks/useLinks.hook.ts

@@ -30,8 +30,13 @@ export const useLinks = (
       return
     }
 
+    const hashIndex = href.indexOf("#")
+    const path = hashIndex === -1 ? href : href.slice(0, hashIndex)
+    const hash = hashIndex === -1 ? undefined : href.slice(hashIndex + 1)
+
     noteEventBus.emit({
-      path: href,
+      path,
+      hash,
       currentNoteSHA: toValue(sha),
       user: store.user,
       repo: store.repo