ci: add a Windows lane for the unit/typecheck/build suite

The pure-logic code carries real win32 branches (shell parsing, WSL path
projection, the PowerShell installer) that mock-injection tests alone
cannot validate. Mirror the ci job on windows-latest (Git Bash as the
step shell) for typecheck / test / build / consumer-type-surface; the
plugin-mount lane (real DSH + Playwright) stays ubuntu-only.

check-consumer-types.sh: force MSYS winsymlinks:nativestrict so Git
Bash's ln -s creates real symlinks instead of deep-copying the repo
(node_modules + full .git history) — inert on Linux/macOS.

scripts/check-consumer-types.sh

@@ -10,6 +10,13 @@
 set -euo pipefail
 cd "$(dirname "$0")/.."
 
+# Git Bash (MSYS) `ln -s` deep-copies directories by default — copying this
+# repo (node_modules + full .git history) would be catastrophic. Force real
+# native symlinks instead: the GitHub Windows runners (Developer Mode, admin
+# user) can create them, and nativestrict makes ln fail loudly rather than
+# silently falling back to a copy. Inert on Linux/macOS.
+export MSYS="winsymlinks:nativestrict"
+
 # The check reads the BUILT declaration surface (lib/types) — fail loudly
 # instead of silently passing when the build output is missing.
 if [ ! -f lib/types/client/service.d.ts ]; then