GitHub `#NNN` issue/PR refs duplicate and break URL on sync

Affected: Plane Cloud, official GitHub integration. See also: meta-issue on destructive overwrite (issue 01).

Symptom

GitHub issue/PR references in a body or comment are corrupted in three distinct ways after a GH→Plane import + Plane→GH round-trip.

Input (GH markdown): #146

Plane stored HTML, after one import:

<a class="issue-link js-issue-link" data-id="..."
   href="https://github.com/<owner>/<repo>/issues/146"
   rel="noopener noreferrer"></a><a href="https://github.com/<repo>/issues/146"
   rel="noopener noreferrer"><repo> #146</a>

Pushed back to GH markdown:

[](https://github.com/<owner>/<repo>/issues/146)[<repo> #146](https://github.com/<repo>/issues/146)

Three distinct bugs

1. URL drops the repository owner. <owner>/<repo>/issues/N becomes <repo>/issues/N — i.e. the integration treats the repo name as the owner segment. The resulting link is a 404 on GitHub.
2. Empty anchor emitted alongside the populated anchor. The first <a> has the correct URL but empty link text. The second <a> has the broken URL and the human-readable text.
3. Anchors multiply on subsequent re-imports. We observed up to 7 repeated tokens preceding the final #NNN link for a single reference after 11 consecutive Plane→GH pushes (visible in userContentEdits). Each round-trip appears to accumulate another anchor.

Impact

• Cross-references between issues become unclickable (404).
• Bodies grow on every round-trip; one issue grew from 2133 bytes to 3461 bytes after a single Plane→GH push, and continued to grow on subsequent pushes.

Ask

Preserve #NNN references as bare #NNN text. GitHub auto-renders these natively.

If conversion to a link is desirable, emit the link once, with the correct <owner>/<repo>/issues/N URL form. Do not emit a companion empty anchor.

Reproduction

1. Connect a GitHub repo to a Plane workspace via the official GitHub integration. Set sync to bidirectional.
2. Create a GitHub issue whose body references another issue with #42. Apply the Plane label.
3. Within seconds the Plane work item has stored HTML with the doubled-anchor + wrong-owner-URL pattern shown above.
4. To exercise the destructive Plane→GH push, follow the trigger recipe in meta-issue 01. Re-trigger to observe anchor multiplication.

Start with the official GitHub integration and reproduce the GH→Plane→GH round-trip using a body containing #42, then inspect the reference conversion paths on both sync directions. Done means preserving a bare #NNN reference or emitting one correct owner/repository URL without an empty companion anchor or growth across repeated imports.