feat: enhance community attribute handling in BIRD format. Add validation for community route bodies to ensure correct tuple structure and introduce tests for single-element standard arrays, improving error handling and robustness in community attribute processing.

internal/birdfmt/community_bird_test.go

@@ -21,3 +21,10 @@ func TestRouteCommunityAttrs_LargeJSON(t *testing.T) {
 		t.Fatalf("got %q", s)
 	}
 }
+
+func TestRouteCommunityAttrs_StandardArrayOneElement(t *testing.T) {
+	_, err := RouteCommunityAttrs("", "x", `{"standard":[65000]}`)
+	if err == nil {
+		t.Fatal("expected error for single-element standard pair")
+	}
+}