fix: merge multiple class attributes into single attribute

- codegen.zig: collect class values and output as single merged attribute
- template.zig: respect quoted flag to prevent data lookup for static class values
- Added tests for multiple class merging scenarios

build.zig.zon

@@ -1,6 +1,6 @@
 .{
     .name = .pugz,
-    .version = "0.3.3",
+    .version = "0.3.4",
     .fingerprint = 0x822db0790e17621d, // Changing this has security and trust implications.
     .minimum_zig_version = "0.15.2",
     .dependencies = .{},