fix: serve and train reuse the built image and expose GPUs correctly

- serve.sh/train.sh no longer pass --build on up/run; the build subcommand is the only path that rebuilds
- compose services pin image: astrai:latest so run reuses the existing image instead of triggering a rebuild
- runtime parsers leave CUDA_VISIBLE_DEVICES unset for gpu.devices: all; an empty string hid every GPU inside the container
- server service reserves count: all GPUs so CUDA_VISIBLE_DEVICES performs the only filtering, matching the trainer
- wrapper compose() strips an empty host CUDA_VISIBLE_DEVICES before invoking docker compose

scripts/tools/serve_runtime.py

@@ -78,9 +78,10 @@ def load_runtime(config_path: str) -> dict[str, str]:
         raise ValueError("runtime.gpu.enabled must be a boolean")
 
     devices = gpu.get("devices", "all")
+    visible_devices = None
     if gpu_enabled:
         if devices == "all":
-            visible_devices = ""
+            pass
         elif isinstance(devices, list) and len(devices) == 1:
             text = str(devices[0])
             if not text.isdigit():
@@ -93,7 +94,6 @@ def load_runtime(config_path: str) -> dict[str, str]:
                 "runtime.gpu.devices must be 'all' or a single-device list such as [0]"
             )
     else:
-        visible_devices = ""
         if devices != "all":
             raise ValueError(
                 "runtime.gpu.devices is ignored when runtime.gpu.enabled is false"
@@ -110,9 +110,10 @@ def load_runtime(config_path: str) -> dict[str, str]:
         "SERVE_PARAM_DIR": _path(paths.get("param", "./params"), "param", path.parent),
         "SERVE_GPU_ENABLED": "true" if gpu_enabled else "false",
         "SERVE_DEVICE": device,
-        "CUDA_VISIBLE_DEVICES": visible_devices,
         "CUDA_TAG": str(container.get("cuda_tag", "cu128")),
     }
+    if visible_devices is not None:
+        values["CUDA_VISIBLE_DEVICES"] = visible_devices
 
     for name, value in environment.items():
         if not isinstance(name, str) or not ENV_NAME.fullmatch(name):