fix(docker): bundle only V3 plugins

docker/Dockerfile

@@ -231,13 +231,7 @@ RUN set -eu; \
     plugin_root="$(find /tmp/plugins-src -mindepth 1 -maxdepth 1 -type d -print -quit)"; \
     test -n "${plugin_root}"; \
     mkdir -p /plugins; \
-    cp -a "${plugin_root}/plugins.v2/." /plugins/; \
-    jq -r 'to_entries[] | select(.value.v2 == true) | .key' "${plugin_root}/package.json" | awk '{print tolower($0)}' | \
-    while read -r plugin_id; do \
-        if [ ! -d "/plugins/${plugin_id}" ]; then \
-            cp -a "${plugin_root}/plugins/${plugin_id}" /plugins/; \
-        fi; \
-    done
+    cp -a "${plugin_root}/plugins.v3/." /plugins/
 
 
 # 准备站点资源

tests/test_docker_payload_contract.py

@@ -84,6 +84,13 @@ def test_dockerfile_assigns_each_payload_to_an_independent_stage() -> None:
     assert final.count("COPY --from=ffmpeg ") == 1
     assert "RUN rm -rf /app/frontend-dist" in dockerfile
 
+    plugin_stage_start = dockerfile.index("FROM prepare_payload AS prepare_plugins")
+    plugin_stage_end = dockerfile.index("# 准备站点资源", plugin_stage_start)
+    plugin_stage = dockerfile[plugin_stage_start:plugin_stage_end]
+    assert 'cp -a "${plugin_root}/plugins.v3/." /plugins/' in plugin_stage
+    assert "plugins.v2" not in plugin_stage
+    assert '"${plugin_root}/package.json"' not in plugin_stage
+
 
 def test_plugin_runtime_updates_preserve_host_entrypoint() -> None:
     """更新载荷只迁移插件内容，不得覆盖新版宿主包根兼容入口。"""