fix(explorer): reveal files in the Windows Explorer when the host runs under WSL

[Kerwin75631591]

fix(explorer): reveal files in the Windows Explorer when the host runs under WSL

Problem

The file-tree context menu action "Show in folder" (the built-in Explorer open-with target, kind reveal) does nothing when DSH runs inside WSL2 (e.g. dsh web hosted in Ubuntu on WSL, UI opened from the Windows browser):

• process.platform is 'linux', so the default branch of revealCommand spawns xdg-open <parent-dir>.
• A WSL host has no Linux desktop file manager and typically no xdg-open (spawn fails with ENOENT, which the route deliberately swallows), and even when xdg-open exists it cannot open the Windows desktop's Explorer.
• Net effect: right-click → Show in folder silently does nothing. (The win32/darwin branches were already correct; only the Linux default branch missed the WSL case.)

Change

Detect the WSL runtime (WSL_DISTRO_NAME env or /proc/version containing microsoft) and, for reveal actions, hand the path to the Windows Explorer exactly like the win32 branch:

1. Translate the absolute path with wslpath -w — /mnt/c/... becomes C:\..., Linux-filesystem paths become \\wsl.localhost\<distro>\....
2. Spawn explorer.exe /select,<translated> so the file/directory is selected in Explorer.
3. When launching a .exe opener under WSL, extend the child PATH with /mnt/c/WINDOWS (+ System32) so Windows interop resolves even for hosts started with a slim PATH.

Plain-Linux and native-macOS/Windows behavior is unchanged (revealCommand still defaults to the non-WSL xdg-open branch; URL open-with targets are untouched — out of scope).

Design notes

• The command builders stay pure/testable: wsl and the path translator are injected parameters, defaulting to non-WSL; launchExternal is the only place that consults isWslRuntime() and the real wslpath-based translator.
• Added a unit test with an injected translator so the WSL branch is covered on non-WSL CI hosts (which have no wslpath).

Test plan

• New unit test in tests/open-external.spec.ts covers the WSL reveal branch (injected translator).
• Existing revealCommand linux/win32/darwin tests unchanged and still green.
• Manual, on a real WSL2 host (Ubuntu-24.04, DSH 0.1.2 host in WSL): right-click a workspace file → Show in folder now opens Windows Explorer with the file selected (Linux-fs and /mnt/c paths both verified).