Make native group reorder discriminate singleton fallback

Prescribe inspected and pressed Card C after reverse membership selection. A singleton C drop is unchanged while the group changes order; preserve prior evaluator scope and test the unchanged negative outcome explicitly.

crates/oa-core/examples/process_multiselect_native.rs

@@ -322,7 +322,7 @@ fn generate(out: &Path) -> Result<()> {
             "fixture": "process-multiselect-native-20260923", "ids": ids, "source_entry": bundle.entry,
             "original_oa_steps": ["oa_a", "oa_u", "oa_b", "oa_v", "oa_c"],
             "reordered_oa_steps": ["oa_b", "oa_u", "oa_a", "oa_v", "oa_c"],
-            "gesture": "Select Card C then Shift-select Card A; drag selected card to After Card B",
+            "gesture": "Select Card C then add Card A; Inspect Card C without changing membership, then drag Card C to After Card B",
             "fixed_slots": {"1": "oa_u", "3": "oa_v"},
             "read_only_trial": "02 Read-only preview trial has two qualified tiles of reused_leaf through distinct references",
             "receipt": "Pin baseline.json, manifest.json and generation command externally before interaction. Never replace baseline with a later saved snapshot.",
@@ -435,8 +435,12 @@ mod tests {
         assert!(error.contains("immutable original"), "{error}");
     }
     #[test]
-    fn global_splice_reversed_block_and_primary_only_results_are_rejected() {
+    fn global_splice_reversed_block_and_singleton_c_results_are_rejected() {
         let before = fixture().unwrap();
+        // Native primary/pressed C is already after B, so a singleton C move
+        // is unchanged. Group {C,A} instead puts B before both selected cards.
+        // If A were primary, its singleton result could equal the group result.
+        mismatch(&before, &before);
         for order in [
             ["oa_u", "oa_b", "oa_a", "oa_c", "oa_v"],
             ["oa_b", "oa_u", "oa_c", "oa_v", "oa_a"],