fix: point self-update check at this fork instead of upstream

Rebased's update mechanism (UpdateInfo.parseUpdateData) fetches
release data straight from GitHub Releases API using
ExternalProductResourceUrls.productPageUrl as the repo -- it was
still hardcoded to detachhead/rebased (the upstream project this was
forked from), so this build was offering to "update" itself to
DetachHead's officially published releases, silently overwriting
this fork's own builds/plugins with theirs. Point it at this fork's
own repo instead.

Co-Authored-By: Claude Sonnet 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01VRS3KihAUVwqL5FV4BWgpp

Merge pull request #9 from hackmajoris/ci/fix-release-token-permission

ci: fix release job permissions (Resource not accessible by integration)