Adds atomic claim operation for work queue messages: - New --claim flag on bd update command - Sets assignee to claimer and status to in_progress - Fails with clear error if already claimed by someone else - Works in both daemon and direct modes - Includes comprehensive tests for claim functionality 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>