Enums whose variants hold values

enum Shape { Circle(float), Rect(float, float), Point }; Shape.Circle(2.0) makes one, match names the values
(Circle(r), _ to ignore), exhaustive like plain enums, printing shows Rect(2, 3.5). Underneath it is a struct (tag +
every variant's values), so copying, freeing, methods and valgrind-cleanliness come with it. Also: stray note files removed.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015f73FesGZGYPkmDvUcj6QX

docs/en/for-engineers.md

@@ -428,4 +428,4 @@ test (22 checks).
 - The driver uses `sh` utilities (`rm`, `mkdir`), so it needs a POSIX shell.
 - Generics are monomorphised (code size grows with instantiations); there are no trait bounds, a wrong use is an error
   inside the instantiated body.
-- No payload enums yet (variants carry no data).
+