Simplify Registry release pipeline

[MattBabbage]

Summary

Registry Publication was failing due to insufficient permissions in the Docker Pipeline.
Option 1: increase permissions to actions:write
Option 2: we just trigger on version release as prior.

Going with Option 2 just trigger on version release as its simpler, and is less of a security risk.

Docker image was still published, manual registry publish was run to resolve issue.
Pipeline with internal failure: https://github.com/github/github-mcp-server/actions/runs/18401464561/job/52431533739

Changes

• Updated registry-releaser workflow: Added a 5-minute wait (with 30-second intervals) to check for Docker image availability before proceeding with MCP Registry publication
• Simplified trigger approach: Uses version tag triggers (v*) instead of repository dispatch to avoid requiring elevated permissions

Benefits

✅ Reliability: Registry publication only succeeds when Docker image is confirmed available
✅ Security: No elevated workflow permissions required
✅ Simplicity: Clean parallel execution with built-in coordination
✅ Fail-safe: 5-minute timeout prevents hanging workflows

[Copilot]

Copilot encountered an error and was unable to review this pull request. You can try again by re-requesting a review.

[mattdholloway]

looks good!