Adds a new slot bead type and merge-slot commands for serializing conflict resolution in the merge queue. This prevents "monkey knife fights" where multiple polecats race to resolve conflicts. - Add TypeSlot to bead types - Add Holder field to Issue struct - Add bd merge-slot create/check/acquire/release commands - Add Holder field to UpdateArgs in RPC protocol (gt-4u49x) 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>