Remote executors (local Docker, remote Docker, Sprites) bind-mount the
linux/amd64 agentctl binary into the container. On non-Linux hosts (e.g.
macOS dev installs) running plain \`make build\` produced only the host
binary, so the first Docker session would fail with:
failed to build container config: agentctl linux binary not found
The top-level \`make dev\` already special-cased non-Linux hosts to chain
\`build-agentctl-linux\`, but \`make build\` and \`make start\` skipped it.
Add it as a dependency of the standard backend build so every install
ships a usable linux variant. Cross-compiling agentctl is fast (~1-2s)
and the binary is ~20 MB, so the cost is negligible.
Users who hit the error can run \`make build-backend\` (or \`make build\`
in apps/backend) to regenerate; setting KANDEV_AGENTCTL_LINUX_BINARY
remains a manual override.
José Almeida
ce79aac590