docs: add actions/setup troubleshooting note

Document the requirement for actions/setup directory in release
troubleshooting section.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: Mossaka

docs/releasing.md

@@ -147,6 +147,7 @@ sudo ./dist/cli.js \
    - Docker build errors: Test image builds locally in `containers/` directories
    - GHCR push errors: Ensure `packages: write` permission is granted
    - Permission errors: Ensure repository has `contents: write` permission
+   - Missing `actions/setup`: The githubnext org workflow requires the `actions/setup` directory (synced from gh-aw repo)
 
 ### Binary doesn't work