test(save): cover version mismatch + slug; clean up tmp on move failure

Add loadRejectsIncompatibleVersion test asserting SaveException on schema
version 999, assert derived slug in listReturnsSlotMetadata, and harden
save() to delete the orphaned .tmp file when the non-atomic fallback move
also fails before re-throwing.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Semesterprojekt/src/test/java/thb/jeanluc/adventure/save/SaveServiceTest.java

@@ -45,6 +45,7 @@ class SaveServiceTest {
         List<SaveSlotInfo> slots = svc.list();
         assertThat(slots).hasSize(1);
         assertThat(slots.getFirst().slotName()).isEqualTo("Alpha Run");
+        assertThat(slots.getFirst().slug()).isEqualTo("alpha_run");
         assertThat(slots.getFirst().turn()).isEqualTo(3);
     }
 
@@ -60,4 +61,16 @@ class SaveServiceTest {
         SaveService svc = new SaveService(dir);
         assertThrows(SaveException.class, () -> svc.load("bad"));
     }
+
+    @Test
+    void loadRejectsIncompatibleVersion(@TempDir Path dir) throws Exception {
+        // a syntactically valid SaveData JSON but with a future schemaVersion
+        String json = "{\"schemaVersion\":999,\"worldTitle\":\"X\",\"slotName\":\"v\","
+                + "\"savedAtEpochMillis\":0,\"turn\":0,\"currentRoomId\":\"k\","
+                + "\"visitedRoomIds\":[],\"gold\":0,\"inventoryItemIds\":[],\"flags\":[],"
+                + "\"questStages\":{},\"questCompleted\":[],\"roomItemIds\":{},\"switchStates\":{}}";
+        Files.writeString(dir.resolve("v.json"), json);
+        SaveService svc = new SaveService(dir);
+        assertThrows(SaveException.class, () -> svc.load("v"));
+    }
 }