[test-build] PluginContainer.from_dict drops install metadata during roundtrip

[huanghuoguoguo]

Background

While continuing the SDK test-build coverage work, a runtime container roundtrip test found that PluginContainer.from_dict() does not preserve install metadata emitted by PluginContainer.model_dump().

Reproducer

container = PluginContainer(
    install_source='marketplace',
    install_info={'id': 'tester/demo'},
    ...
)
restored = PluginContainer.from_dict(container.model_dump())

assert restored.install_source == 'marketplace'
assert restored.install_info == {'id': 'tester/demo'}

Expected: serialized container metadata roundtrips.

Actual: from_dict() does not pass install_source or install_info, so the restored container falls back to default empty values.

Risk

• Plugin install provenance can be lost after persistence/cache roundtrip.
• Runtime management, upgrades, diagnostics, or marketplace-origin logic may make decisions with missing metadata.
• model_dump() and from_dict() are not inverse operations.

Test Signal

Locked in test-build as an xfail(strict=True) contract test:

tests/runtime/plugin/test_container.py::test_plugin_container_roundtrip_should_preserve_install_metadata

No source fix is included in the test-build branch.

[huanghuoguoguo]

已在 #65（commit 9723b59）修复。

修复方式：PluginContainer.from_dict 现在恢复 install_source 和 install_info，插件容器 dict roundtrip 不再丢安装来源和安装元数据。

回归用例：tests/runtime/plugin/test_container.py::test_plugin_container_roundtrip_should_preserve_install_metadata。

测试：

• 对应 strict xfail 已取消，回归用例现在正常执行并通过。
• SDK：uv run pytest -> 269 passed, 10 warnings。
• LangBot master E2E：将本地 SDK editable 安装到 master worktree，WebUI 上传安装 qa/plugin-smoke，验证插件安装、Tool/Page 注册、Smoke Page iframe 渲染，以及 page-api /ping 返回 qa-plugin-smoke-page。