[Bug] Windows native directory picker truncates paths: UTF-16 chars with low byte 0x00 (e.g. U+5F00) cause workspace-invalid-path ENOENT

[Xizhi1024]

Environment

• OS: Windows 11, VS Code 1.128.0 (extension-host embedding of the DSH web UI)
• DSH: @deepseek-ai/dsh 0.1.0-rc.6, web profile (dsh-base + dsh-web-app)
• Entry point: DSH web GUI workspace switcher using the native directory picker

Steps to reproduce

1. Start the DSH web UI (dsh web).
2. Open the workspace switcher and use the native directory picker ("Select Workspace Directory").
3. Select a directory whose name ends with a character whose UTF-16 code unit has a low byte of 0x00 - e.g. a folder named 慢开 (U+6162 U+5F00).

Actual result

Workspace creation fails with:

workspace create failed: workspace-invalid-path: cannot create a workspace at "D:\my_work_project\Dungs_1\慢": ENOENT: no such file or directory, realpath 'D:\my_work_project\Dungs_1\慢'

The picked path was D:\my_work_project\Dungs_1\慢开 - the final character 开 (U+5F00) was silently dropped, so fs.realpath correctly rejects the truncated, non-existent path. ASCII paths work fine.

Root cause

The readUtf16 helper in the Win32 dialog worker (dsh-host-directory-picker-native, bundled lib/worker.cjs):

function readUtf16(koffi, address) {
    const bytes = Buffer.from(koffi.view(address, 32768));
    let end = 0;
    while (end + 1 < bytes.length && bytes[end] !== 0) end += 2;
    return bytes.toString("utf16le", 0, end);
}

The loop treats a single zero byte at an even offset as the NUL terminator, but a UTF-16LE code unit is two bytes. Every BMP character whose code point is of the form U+XX00 (low byte 0x00) terminates the string early: 开 = U+5F00 encodes as 00 5F, 一 = U+4E00 as 00 4E, 怀 = U+6000 as 00 60. Characters like 慢 (U+6162), 快 (U+5FEB) or 持 (U+6301) are NOT affected; in the repro above, 慢开 loses only 开 and leaves 慢.

Suggested fix

Terminate only on a complete zero code unit:

while (end + 1 < bytes.length && (bytes[end] !== 0 || bytes[end + 1] !== 0)) end += 2;

or equivalently test bytes.readUInt16LE(end) !== 0.

Affected components

• dsh-host-directory-picker-native (lib/worker.cjs, path extraction)
• dsh-workspace (realpathNormalize rejects the truncated input with ENOENT - correct given the bad input)
• dsh-host-apiproxy (surfaces the workspace-invalid-path RPC error)

Workaround

Launch dsh with the intended workspace as the process cwd (the workspace root follows the launch directory), avoiding the in-UI workspace switcher for such paths.

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中文摘要

• 环境：Windows 11 / VS Code 1.128.0 / @deepseek-ai/dsh 0.1.0-rc.6（web profile）。
• 复现：web UI 工作区切换 → 原生目录选择器选中以“开”（U+5F00）结尾的目录（如“慢开”）。
• 现象：报 workspace-invalid-path: ENOENT，报错路径末尾的“开”被截断（“慢开”→“慢”）。
• 根因：dsh-host-directory-picker-native 的 lib/worker.cjs 中 readUtf16 以单字节 0x00 判断字符串结束，而“开”的 UTF-16LE 编码为 00 5F，低字节恰为 0x00，循环提前终止，路径被截断。受影响的是码点形如 U+XX00 的字符（如 一=U+4E00、开=U+5F00、怀=U+6000）；慢（U+6162）、快（U+5FEB）、持（U+6301）不受影响。纯 ASCII 路径不受影响。
• 建议修复：仅当整个 UTF-16 code unit 为零（bytes[end] !== 0 || bytes[end+1] !== 0）时才终止。
• 规避：以目标目录为 cwd 启动 dsh，绕开 UI 内的工作区切换。