Host Directory Picker Native

The **native-OS-chooser backend** of the [directory-picker seam](../directory-picker/README.md): `NativeDirectoryPicker` registers `ctx.directoryPicker` with the `native` capability, whose `pick(signal)` opens one native chooser per call and resolves the chosen absolute path (`null` on cancel). Platform tools run without a shell: `osascript` on macOS and Zenity with a KDialog fallback on Linux; the caller's abort terminates the native process. Windows opens the modern `IFileOpenDialog` in a spawned child process — a koffi-driven COM conversation on the child's main thread with the best thread DPI awareness the host accepts (per-monitor-v2 first), aborted by posting `WM_CLOSE` to the dialog thread. Only viable when the operator sits at the host's display — remote deployments compose [`-browse`](../directory-picker-browse/README.md) instead. The command boundary (`DirectoryPickerRunner`) and platform facts are injectable. The shared no-shell subprocess runner lives in [`dsh-native-command`](../../util/native-command/README.md).

• 适用 Agent：DeepSeek Harness
• 适配模型：DeepSeek

@deepseek-ai/dsh-host-directory-picker-native

暂无通过审核、可复现的同任务 A/B 运行证据；本档案仅证明来源可信，不代表实测有效。