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

EOF

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

internal/update/store_other.go

@@ -0,0 +1,6 @@
+//go:build !windows
+
+package update
+
+// IsStorePackaged is false outside Windows (no Microsoft Store / MSIX package identity).
+func IsStorePackaged() bool { return false }