Ignore .gstack/ tooling artifacts

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Anthony Green2026-07-07 10:39:00 -0400 00a304a54f7c45dd450411cd58928553ce0db3dc
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>