fix fragile hak packing

internal/topdata/top_package.go

@@ -211,11 +211,12 @@ func collectTopPackageResources(p *project.Project, compiled2DADir string) ([]er
 			if d.IsDir() {
 				return nil
 			}
-			if strings.HasPrefix(filepath.Base(path), ".") {
-				return nil
+			rel, err := filepath.Rel(assetsDir, path)
+			if err != nil {
+				return err
 			}
-			if strings.EqualFold(filepath.Ext(path), ".md") {
-				return nil // docs (AGENTS.md, README.md, ...) are never HAK resources
+			if skipTopPackageAsset(rel) {
+				return nil
 			}
 			resource, err := topPackageResourceFromPath(path)
 			if err != nil {
@@ -388,6 +389,25 @@ func newestMatchingAutogenOverrideInput(scanRoot string, include []string) (time
 	return newest, newestPath, nil
 }
 
+// skipTopPackageAsset reports whether a file under assets/ is not a HAK
+// resource and must be ignored by both validation and packing: anything in a
+// hidden or underscore-prefixed directory (working dirs like _candidates),
+// hidden files, docs, and any extension that is not a known NWN ResType
+// (erf.extensionTypes is the whitelist). rel is the path relative to assets/.
+func skipTopPackageAsset(rel string) bool {
+	for _, part := range strings.Split(filepath.ToSlash(rel), "/") {
+		if strings.HasPrefix(part, ".") || strings.HasPrefix(part, "_") {
+			return true
+		}
+	}
+	if strings.EqualFold(filepath.Ext(rel), ".md") {
+		return true
+	}
+	ext := strings.TrimPrefix(strings.ToLower(filepath.Ext(rel)), ".")
+	_, ok := erf.HAKResourceTypeForExtension(ext)
+	return !ok
+}
+
 func topPackageResourceFromPath(path string) (erf.Resource, error) {
 	extension := strings.TrimPrefix(strings.ToLower(filepath.Ext(path)), ".")
 	resourceType, ok := erf.HAKResourceTypeForExtension(extension)