Add bead gate type for cross-rig bead dependencies: - await_type=bead with await_id=<rig>:<bead-id> format - Add `bd gate check` command to evaluate open gates - Support --type=bead to check only bead gates - Support --dry-run to preview without closing - Gate resolves when target bead is closed Closes bd-w3rh 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>