20091a9c26
Add Podman as a rootless/daemonless sandbox backend alongside Docker, Multipass and Local, and wire Goose in as the default agentic harness for the granted `!task` path (bridge execs `<engine> exec <name> goose run` and streams output to chat; auto-degrades to the simple one-shot injector when goose is absent). Add an optional GUI sandbox track (XFCE + TigerVNC + websockify/noVNC on :6080) summoned via `/sbx <engine> gui`, plus container-side provisioning in sandbox-bootstrap.sh and a host-side ensure-podman.sh prereq helper. Refresh the in-app command help to the backend-led `/sbx <engine> [gui]` grammar and minor ui tweaks. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>