Six test runner scripts at tests/: run-rust, run-godot, run-ipc-fixtures, run-ipc-protocol, run-ipc-integration, run-all. Plus run-ipc-benchmark for Layer 3 timing. All produce structured JSON stdout, support --filter, and exit 0/non-zero. Makefile targets updated to delegate to scripts. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>