Add Store MSIX packaging and dark/light theme for 2.9.0.

EOF

Co-authored-by: Cursor <cursoragent@cursor.com>

internal/update/store_windows.go

@@ -0,0 +1,49 @@
+//go:build windows
+
+package update
+
+import (
+	"sync"
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+)
+
+const (
+	appModelErrorNoPackage   = 15700 // APPMODEL_ERROR_NO_PACKAGE
+	errorInsufficientBuffer  = 122   // ERROR_INSUFFICIENT_BUFFER
+)
+
+var (
+	storeOnce     sync.Once
+	storePackaged bool
+)
+
+// IsStorePackaged reports whether this process has an MSIX / Store package identity.
+// Store builds must not self-update (Store owns updates).
+func IsStorePackaged() bool {
+	storeOnce.Do(func() {
+		storePackaged = detectStorePackage()
+	})
+	return storePackaged
+}
+
+func detectStorePackage() bool {
+	mod := windows.NewLazySystemDLL("kernel32.dll")
+	proc := mod.NewProc("GetCurrentPackageFullName")
+	if err := proc.Find(); err != nil {
+		return false
+	}
+	var n uint32
+	r, _, _ := proc.Call(uintptr(unsafe.Pointer(&n)), 0)
+	switch r {
+	case appModelErrorNoPackage:
+		return false
+	case errorInsufficientBuffer:
+		return true
+	case 0:
+		return n > 0
+	default:
+		return false
+	}
+}