Support running host processes alongside VMs (#482)

* Regenerate .pb with protoc-gen-go v1.36.11

* Support running host processes alongside VMs

* Replace existing host processes when starting a set

internal/worker/hostprocess/process_test.go

@@ -0,0 +1,58 @@
+//nolint:noctx,testpackage,usetesting // Preserve the socket-path tests and their required short /var/tmp paths.
+package hostprocess
+
+import (
+	"net"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestShortenControlSocketPath(t *testing.T) {
+	// Create a control socket path that exceeds macOS's 104-byte limit
+	const controlSocketName = "control.sock"
+
+	vmDir := filepath.Join(t.TempDir(), strings.Repeat("v", 104))
+	require.NoError(t, os.MkdirAll(vmDir, 0o700))
+
+	controlSocketPath := filepath.Join(vmDir, controlSocketName)
+	require.Greater(t, len(controlSocketPath), 104)
+
+	// Create Orchard's short per-process runtime directory
+	runtimeDir, err := os.MkdirTemp("/var/tmp", "orchard-hp-test-")
+	require.NoError(t, err)
+	t.Cleanup(func() {
+		require.NoError(t, os.RemoveAll(runtimeDir))
+	})
+
+	// Shorten the control socket path and verify the resulting alias
+	shortControlSocketPath, err := shortenControlSocketPath(runtimeDir, controlSocketPath)
+	require.NoError(t, err)
+	require.Equal(t, filepath.Join(runtimeDir, "vm.sock"), shortControlSocketPath)
+	require.Less(t, len(shortControlSocketPath), 104)
+
+	// Model Tart binding the socket relative to the long VM directory
+	t.Chdir(vmDir)
+
+	listener, err := net.Listen("unix", controlSocketName)
+	require.NoError(t, err)
+	t.Cleanup(func() {
+		require.NoError(t, listener.Close())
+	})
+
+	// Model the host process running from Orchard's runtime directory
+	t.Chdir(runtimeDir)
+
+	// Verify connecting through the long absolute path fails
+	connection, err := net.Dial("unix", controlSocketPath)
+	require.Error(t, err)
+	require.Nil(t, connection)
+
+	// Connect to Tart's control socket through Orchard's short alias
+	connection, err = net.Dial("unix", shortControlSocketPath)
+	require.NoError(t, err)
+	require.NoError(t, connection.Close())
+}