Pin format.ps1 to Git Bash on Windows

A bare `bash` on Windows can resolve to the WSL launcher
(System32\bash.exe) ahead of Git Bash, running the pre-commit hook
inside a Linux distro. There the CRLF-checked-out script fails to parse
("$'\r': command not found"), and even with clean line endings the WSL
path would install a Linux dotnet-format instead of the Windows one.
Resolve Git Bash from git.exe's install location instead, the same
CRLF-tolerant shell git itself uses to run the hook; non-Windows
platforms keep using plain bash.

Assisted-by: Claude:claude-fable-5:Claude Code

BuildTools/format.ps1

@@ -5,7 +5,17 @@ $ErrorActionPreference = 'Stop'
 $env:OPENSSL_ENABLE_SHA1_SIGNATURES = '1'
 Push-Location (Join-Path $PSScriptRoot '..')
 try {
-    bash BuildTools/pre-commit --format
+    # On Windows, a bare `bash` can resolve to the WSL launcher (System32\bash.exe),
+    # which runs the hook inside a Linux distro where the CRLF-checked-out script
+    # cannot even be parsed. Pin to Git Bash, the same CRLF-tolerant shell git
+    # itself uses to run the pre-commit hook.
+    $bash = if ($IsWindows) {
+        Join-Path (Split-Path (Split-Path (Get-Command git).Source)) 'bin\bash.exe'
+    }
+    else {
+        'bash'
+    }
+    & $bash BuildTools/pre-commit --format
 }
 finally {
     Pop-Location