refactor: move runtime parsers into scripts/docker

- serve_runtime.py and train_runtime.py are host-side Docker helpers, so they join train-entrypoint.sh and lib/ under scripts/docker/
- scripts/tools/ now contains only in-container CLIs
- update wrapper call sites, test import, and docker guide references

scripts/train.sh

@@ -51,7 +51,7 @@ load_config() {
         die "PyYAML is required on the host (install python3-yaml)"
 
     local exports
-    exports="$(python3 "${ROOT_DIR}/scripts/tools/train_runtime.py" exports "${CONFIG_FILE}")" ||
+    exports="$(python3 "${ROOT_DIR}/scripts/docker/train_runtime.py" exports "${CONFIG_FILE}")" ||
         die "Failed to load runtime configuration"
     eval "${exports}"
     validate_job_name "${TRAIN_JOB_NAME}"
@@ -148,7 +148,7 @@ runtime_environment_args() {
     local pair
     while IFS= read -r -d '' pair; do
         RUNTIME_ENV_ARGS+=(--env "${pair}")
-    done < <(python3 "${ROOT_DIR}/scripts/tools/train_runtime.py" environment "${CONFIG_FILE}")
+    done < <(python3 "${ROOT_DIR}/scripts/docker/train_runtime.py" environment "${CONFIG_FILE}")
 }
 
 start_training() {