Adds bd doctor --server to diagnose Dolt server mode connections: - Server reachability (TCP connect to host:port) - Dolt version check (verifies it is Dolt, not vanilla MySQL) - Database exists and is accessible - Schema compatible (can query beads tables) - Connection pool health metrics Supports --json for machine-readable output. Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>