CI: bump Windows Swift toolchain to 6.3.3 for VS 2026 / MSVC 14.51

The windows-latest runner now ships Visual Studio 18 (2026) with MSVC
14.51, whose intrinsics headers the Swift 6.0.2 clang can't compile into
a module (_visualc_intrinsics -> ucrt -> SwiftOverlayShims). Bump only the
Windows toolchain to current stable 6.3.3; its clang parses the new
headers. Package stays swift-tools-version:5.9, so language mode and
sources are unchanged; Linux/macOS jobs are untouched.

Author: douglas-carmichael

.github/workflows/clusterdaemon.yml

@@ -34,12 +34,18 @@ jobs:
         with:
           swift-version: '6.0.2'
 
+      # Windows pins a NEWER toolchain than Linux on purpose: the windows-latest
+      # runner ships Visual Studio 18 (2026) with MSVC 14.51, whose intrinsics
+      # headers the older Swift 6.0.2 clang can't compile into a module (fails
+      # building _visualc_intrinsics -> ucrt -> SwiftOverlayShims). A current
+      # toolchain has a clang new enough to parse them. The package stays
+      # swift-tools-version:5.9, so the language mode is unchanged.
       - name: Set up Swift (Windows)
         if: runner.os == 'Windows'
         uses: compnerd/gha-setup-swift@main
         with:
-          branch: swift-6.0.2-release
-          tag: 6.0.2-RELEASE
+          branch: swift-6.3.3-release
+          tag: 6.3.3-RELEASE
 
       - name: Swift version
         run: swift --version