ci(windows): fix VS2026 shared-link test vcvars path

The VS2026 shared-library linking test searched for vcvars64.bat under
"Microsoft Visual Studio\2026", but VS 2026 installs under a version folder
("Microsoft Visual Studio\18\Enterprise"). The find returned nothing, so the
step fell through and exited 1 even though the DLL built fine. Search the whole
Visual Studio directory instead, matching the VS2022 linking test.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: wysaid

.github/workflows/windows-build.yml

@@ -396,8 +396,10 @@ jobs:
         }
         EOF
         
-        # Find Visual Studio 2026 compiler
-        VCVARS_PATH=$(find "/c/Program Files/Microsoft Visual Studio/2026" -name "vcvars64.bat" 2>/dev/null | head -n1)
+        # Find the Visual Studio compiler. The VS 2026 install lives under a version
+        # folder ("...\Microsoft Visual Studio\18\..."), not a "2026" year folder, so
+        # search the whole VS directory rather than hard-coding the name.
+        VCVARS_PATH=$(find "/c/Program Files/Microsoft Visual Studio" -name "vcvars64.bat" 2>/dev/null | head -n1)
         
         if [ -n "$VCVARS_PATH" ]; then
           echo "Using Visual Studio 2026 environment from: $VCVARS_PATH"