ai(rules[AGENTS]) Require Attributes on classes with fields

why: autodoc renders every NamedTuple and dataclass field regardless of
whether it is described, so an undocumented field reaches the API docs as
"Alias for field number 0" or as a bare entry. Seven such stubs are live
on the published site today, and nothing in the gates catches them.

what:
- Require an Attributes section covering every field, with an example
- Note that partial coverage still ships stubs for the rest

Author: tony

AGENTS.md

@@ -156,6 +156,25 @@ type
 """
 ```
 
+**Classes with fields** — `NamedTuple`, dataclasses — document every field in
+an `Attributes` section:
+
+```python
+class ConfigFileResolution(t.NamedTuple):
+    """Outcome of deciding which config file ``add`` should write to.
+
+    Attributes
+    ----------
+    path : pathlib.Path | None
+        Config file to write to, or ``None`` when the choice was ambiguous.
+    """
+```
+
+Autodoc renders every field whether or not you describe it, so an
+undocumented `NamedTuple` field ships to the API docs as "Alias for field
+number 0" and a dataclass field ships bare. Document all of them — a class
+with three fields and two documented still ships a stub for the third.
+
 ### Doctests
 
 **All functions and methods MUST have working doctests.** Doctests serve as both documentation and tests.