feat: add Carla plugin host stubs and integration plan

client/src/carla_host.h

@@ -0,0 +1,14 @@
+#ifndef CARLA_HOST_H
+#define CARLA_HOST_H
+
+#include <stdbool.h>
+
+/* All functions return -1 on error, 0 on success (except carla_load which returns 0 on success and sets *out_id) */
+
+int carla_load(const char *binary, const char *plugin_id, int *out_id);
+int carla_unload(int id);
+int carla_connect(int id, const char *port_name, const char *looper_port);
+int carla_disconnect(const char *from, const char *to);
+void carla_set_bypass(int id, bool bypass);
+
+#endif