Refine Windows Dev Drive setup

Incorporate the uv Dev Drive setup pattern by remounting newly-created Dev Drive VHDs after filter changes, using the configured temp directory for Bazel repo contents cache, and moving Cargo target output onto the selected fast Windows drive while preserving the default target path on other platforms.

Co-authored-by: Codex <noreply@openai.com>

.github/scripts/setup-dev-drive.ps1

@@ -44,6 +44,15 @@ if (Test-Path "D:\") {
 
         Invoke-BestEffort { fsutil devdrv trust $Drive } "Trusting Dev Drive $Drive"
         Invoke-BestEffort { fsutil devdrv enable /disallowAv } "Disabling AV filter attachment for Dev Drives"
+        try {
+            Dismount-VHD -Path $VhdPath
+            Mount-VHD -Path $VhdPath | Out-Null
+        } catch {
+            Write-Warning "Remounting Dev Drive $Drive failed: $($_.Exception.Message)"
+            if (-not (Test-Path "$Drive\")) {
+                throw
+            }
+        }
         Invoke-BestEffort { fsutil devdrv query $Drive } "Querying Dev Drive $Drive"
 
         Write-Output "Using Dev Drive at $Drive"
@@ -55,8 +64,12 @@ if (Test-Path "D:\") {
 $Tmp = "$Drive\codex-tmp"
 New-Item -Path $Tmp -ItemType Directory -Force | Out-Null
 
+$CargoTargetDir = "$Drive\codex-cargo-target"
+New-Item -Path $CargoTargetDir -ItemType Directory -Force | Out-Null
+
 @(
     "DEV_DRIVE=$Drive"
+    "CARGO_TARGET_DIR=$CargoTargetDir"
     "TMP=$Tmp"
     "TEMP=$Tmp"
 ) | Out-File -FilePath $env:GITHUB_ENV -Encoding utf8 -Append