fix(docker): drop no-op userns_mode (NAS has no userns-remap)

The chown failures were never a userns-remap issue (the NAS daemon has no
userns-remap configured) — they were the .git-only chown leaving the working
tree root-owned, fixed separately. userns_mode:host on the orchestrator alone
was a no-op at best and a latent footgun (orchestrator un-remapped while agents
are not) if remap were ever enabled. Keep the uv-in-runner + env=production.

docker-compose.yml

@@ -242,10 +242,6 @@ services:
       # Production environment selects structlog's JSONRenderer (machine-
       # parseable logs) over the dev ConsoleRenderer.
       ROBOCO_ENVIRONMENT: production
-    # Run in the host user namespace so the orchestrator's chown of cloned
-    # workspaces to the agent uid (1000) isn't blocked by docker's userns
-    # remap (which would shift ownership out of the expected uid range).
-    userns_mode: "host"
     volumes:
       # Docker socket - allows spawning agent containers
       - /var/run/docker.sock:/var/run/docker.sock