docs: explain match assertions and annotation type distinctions

crates/core/tests/builtins.rs

@@ -148,8 +148,10 @@ fn dictionaries_keep_order_and_first_key_and_own_keys_and_values() {
     );
     assert_eq!(vm.dict_items(dict).unwrap()[0].0, Value::Object(key));
     assert_eq!(vm.dict_items(dict).unwrap().len(), 2);
+    // 字典覆盖旧值后，old 已无任何拥有根，访问必须报告失效句柄。
     assert!(matches!(vm.object(old), Err(VmError::InvalidHandle)));
     assert!(vm.dict_delete(dict, &text("answer")).unwrap());
+    // 删除 answer 同时释放保留的首键对象，等价 Text 键不会替它延长寿命。
     assert!(matches!(vm.object(key), Err(VmError::InvalidHandle)));
     assert!(!vm.dict_delete(dict, &text("missing")).unwrap());
     vm.dict_clear(dict).unwrap();
@@ -227,6 +229,7 @@ fn cells_share_rebinding_distinguish_empty_and_none_and_keep_stable_objects() {
     vm.cell_set(cell, Value::Object(child)).unwrap();
     assert_eq!(vm.ref_count(child).unwrap(), 1);
     vm.cell_clear(cell).unwrap();
+    // 清空 Cell 归还子对象最后的内部边，child 不能仍然可访问。
     assert!(matches!(vm.object(child), Err(VmError::InvalidHandle)));
     assert_eq!(vm.cell_get(cell), Err(VmError::EmptyCell));
 }