- Add mutex protection for global registry state - Cache loaded config paths to avoid redundant file reads - Add ResetRegistryForTesting() for test isolation - Add BuildResumeCommand() for agent-specific session resume - Add SupportsSessionResume() and GetSessionIDEnvVar() helpers Fixes: gt-sn610, gt-otgn3, gt-r2eg1 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>