typecheck: preserve text operands in arithmetic diagnostics

docs/ADVANCED_STATIC_TYPING.md

@@ -89,6 +89,18 @@ Type mismatch for field backup.score: expected NUMBER, but this value looks like
 
 This remains limited to direct assignments through simple alias chains; control-flow and complex object-flow analysis are still planned.
 
+Text operands are also identified when they appear in subtraction, multiplication, or division expressions. This catches a common beginner mistake such as subtracting a text field from a number field:
+
+```claro
+SET player.score player.score - player.name
+```
+
+```text
+Type mismatch for field player.score: expected NUMBER, but this value looks like TEXT.
+```
+
+The expression checker still deliberately reports only the type it can infer; full operator-specific rules remain future work.
+
 `CHECK TYPE` also preserves TEXT field metadata through the same chained aliases:
 
 ```claro