Use `D:` drive for Windows CI (#10180)

When using the standard Windows runners (as opposed to the _larger_
GitHub runners), an undocumented `D:` drive is available and performant.
We can save some money on by using this on a standard runner instead of
a larger runner with an ReFS drive. Switching to the `D:` drive was not
acceptable for `cargo test` >25m runtime.

Inspired by https://github.com/pypa/pip/pull/13129
See https://github.com/actions/runner-images/issues/8755

Timings (grain of salt — GitHub is super noisy):

- clippy: 2m 18s -> 2m 11s
- build binary: 2m 3s -> 2m 35s
- trampoline check (x86-64): 2m 32s -> 1m 50s (other architectures
similar)
- trampoline test (x86-64): 4m 12s -> 6m 7s
- trampoline test (i686): 6m 44s -> 5m 35s

.github/workflows/ci.yml

@@ -116,7 +116,7 @@ jobs:
     timeout-minutes: 15
     needs: determine_changes
     if: ${{ github.repository == 'astral-sh/uv' && !contains(github.event.pull_request.labels.*.name, 'no-test') && (needs.determine_changes.outputs.code == 'true' || github.ref == 'refs/heads/main') }}
-    runs-on: github-windows-2025-x86_64-16
+    runs-on: windows-latest
     name: "cargo clippy | windows"
     steps:
       - uses: actions/checkout@v4
@@ -324,7 +324,7 @@ jobs:
     timeout-minutes: 15
     needs: determine_changes
     if: ${{ github.repository == 'astral-sh/uv' && !contains(github.event.pull_request.labels.*.name, 'no-test') && (needs.determine_changes.outputs.code == 'true' || github.ref == 'refs/heads/main') }}
-    runs-on: github-windows-2025-x86_64-16
+    runs-on: windows-latest
     name: "check windows trampoline | ${{ matrix.target-arch }}"
     strategy:
       fail-fast: false
@@ -517,7 +517,7 @@ jobs:
     needs: determine_changes
     timeout-minutes: 10
     if: ${{ github.repository == 'astral-sh/uv' && !contains(github.event.pull_request.labels.*.name, 'no-test') && (needs.determine_changes.outputs.code == 'true' || github.ref == 'refs/heads/main') }}
-    runs-on: github-windows-2025-x86_64-8
+    runs-on: windows-latest
     name: "build binary | windows"
     steps:
       - uses: actions/checkout@v4

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

@@ -1,32 +1,46 @@
-# This creates a 20GB dev drive, and exports all required environment
-# variables so that rustup, uv and others all use the dev drive as much
-# as possible.
-$Volume = New-VHD -Path C:/uv_dev_drive.vhdx -SizeBytes 20GB |
-					Mount-VHD -Passthru |
-					Initialize-Disk -Passthru |
-					New-Partition -AssignDriveLetter -UseMaximumSize |
-					Format-Volume -DevDrive -Confirm:$false -Force
+# Configures a drive for testing in CI.
 
-$Drive = "$($Volume.DriveLetter):"
+# When not using a GitHub Actions "larger runner", the `D:` drive is present and
+# has similar or better performance characteristics than a ReFS dev drive.
+# Sometimes using a larger runner is still more performant (e.g., when running
+# the test suite) and we need to create a dev drive. This script automatically
+# configures the appropriate drive.
 
-# Set the drive as trusted
-# See https://learn.microsoft.com/en-us/windows/dev-drive/#how-do-i-designate-a-dev-drive-as-trusted
-fsutil devdrv trust $Drive
+# Note we use `Get-PSDrive` is not sufficient because the drive letter is assigned.
+if (Test-Path "D:\") {
+    Write-Output "Using existing drive at D:"
+    $Drive = "D:"
+} else {
+	# The size (20 GB) is chosen empirically to be large enough for our
+	# workflows; larger drives can take longer to set up.
+	$Volume = New-VHD -Path C:/uv_dev_drive.vhdx -SizeBytes 20GB |
+						Mount-VHD -Passthru |
+						Initialize-Disk -Passthru |
+						New-Partition -AssignDriveLetter -UseMaximumSize |
+						Format-Volume -DevDrive -Confirm:$false -Force
 
-# Disable antivirus filtering on dev drives
-# See https://learn.microsoft.com/en-us/windows/dev-drive/#how-do-i-configure-additional-filters-on-dev-drive
-fsutil devdrv enable /disallowAv
+	$Drive = "$($Volume.DriveLetter):"
 
-# Remount so the changes take effect
-Dismount-VHD -Path C:/uv_dev_drive.vhdx
-Mount-VHD -Path C:/uv_dev_drive.vhdx
+	# Set the drive as trusted
+	# See https://learn.microsoft.com/en-us/windows/dev-drive/#how-do-i-designate-a-dev-drive-as-trusted
+	fsutil devdrv trust $Drive
 
-# Show some debug information
-Write-Output $Volume
-fsutil devdrv query $Drive
+	# Disable antivirus filtering on dev drives
+	# See https://learn.microsoft.com/en-us/windows/dev-drive/#how-do-i-configure-additional-filters-on-dev-drive
+	fsutil devdrv enable /disallowAv
 
-# Configure a temporary directory
-$Tmp = "$($Drive)/uv-tmp"
+	# Remount so the changes take effect
+	Dismount-VHD -Path C:/uv_dev_drive.vhdx
+	Mount-VHD -Path C:/uv_dev_drive.vhdx
+
+	# Show some debug information
+	Write-Output $Volume
+	fsutil devdrv query $Drive
+
+    Write-Output "Using Dev Drive at $Volume"
+}
+
+$Tmp = "$($Drive)\uv-tmp"
 
 # Create the directory ahead of time in an attempt to avoid race-conditions
 New-Item $Tmp -ItemType Directory