feat(windows): the ludic CLI and ludic bundle on Windows

The CLI's shell commands go through shell(), which is run() on POSIX and a
scratch script handed to Git for Windows' bash on Windows (exit codes read
directly there). compile_app links through `ludicc -o` on Windows, ludic run
starts the .exe, and ludic-dev build and ensure_ludicc assemble
selfhost/ludicc.win.seed.ll, which ludic-dev reseed now writes beside the
macOS seed. ludic bundle makes build/<name>/ with a GUI-subsystem exe carrying
the .ico beside `app icon` as an llvm-rc resource, game.lpak and packs.index;
ludicc gains --gui and --link, and quotes its whole link line for cmd.exe.

Verified: ludic-dev test 135/135, selfhost-test 32/32; on the PC a checkout
bootstraps from the Windows seed, ludic-dev build makes the toolchain, and
`ludic bundle` makes build/Maroon Lake/, which runs from its own folder.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tools/ludic-cli/assets.ludic

@@ -58,10 +58,10 @@ function cmd_fetch_assets() -> int {
       continue
     }
     print(`fetch {rel}`)
-    run(`mkdir -p "$(dirname {dest})"`)
+    shell(`mkdir -p "$(dirname {dest})"`)
     if not shq(`curl -sSL --retry 3 -o {dest} {url}`) {
       err(`fetch-assets: cannot fetch {rel}\n`)
-      run(`rm -f {dest}`)
+      shell(`rm -f {dest}`)
       failed += 1
     } else {
       got += 1