review: require .2da suffix on race feats tables, shrink rule test compare

Review of #94 branch: tighten racialUsableFeatRules to match the spec's
'race_feat_*.2da' (prefix alone would admit a non-2DA dataset), and
replace the test's length-check-plus-loop with one reflect.DeepEqual.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

internal/topdata/native.go

@@ -4154,7 +4154,7 @@ func racialUsableFeatRules(collected []nativeCollectedDataset) []project.TopData
 	seen := map[string]struct{}{}
 	rules := []project.TopDataClassFeatGlobalRule{}
 	for _, ds := range collected {
-		if !strings.HasPrefix(ds.Dataset.OutputName, "race_feat_") {
+		if !strings.HasPrefix(ds.Dataset.OutputName, "race_feat_") || !strings.HasSuffix(ds.Dataset.OutputName, ".2da") {
 			continue
 		}
 		for _, row := range ds.Rows {