* fix(agents): serialize sandbox provisioning * test(docker): add sandbox browser sidecar e2e * fix(ci): register sandbox browser e2e entrypoint * fix(ci): restore code mode matrix checks
* feat(agents): add code mode model acceptance matrix * fix(qa): emit canonical Code Mode matrix evidence * fix(qa): reserve code mode matrix output safely * fix(qa): require fresh matrix builds * fix(qa): protect matrix evidence paths