DL-580

Two backends sit behind one agent vcs_* tool surface, chosen per repo: the RIG-5558 git backend ships unchanged for repos on GitHub, and Saiph serves Saiph repos through the saiph CLI, where agents have no GitHub egress and only trunk is mirrored to GitHub as derived git commits; the tools, the Runner backend pick and the web UI hooks stay in Compass, and Saiph stays in its own repo.

Status: Active (design, 2026-10-18)