fix(types): P2 — wire _MixinBase + col() across sqlmodel_repo; suppress pydantic/SQLModel column typing false positives

- Add _MixinBase abstract class to _helpers.py: declares _session(),
  _deserialize_attacker(), _assert_pending(), _check_and_bump_version(),
  and list_running_topology_deckies() so mypy can see cross-mixin contracts
- Add _require(val, msg) helper for narrowing T | None → T
- Inherit _MixinBase in all 26 leaf mixin classes
- Wrap SQLAlchemy column method calls (.is_(), .like(), .notin_(), .in_(),
  .contains()) with col() from sqlmodel — fixes attr-defined false positives
  caused by pydantic plugin typing class-level fields as Python value types
- Wrap select(Model.field) with select(col(Model.field)) for column projections
- Add pyproject.toml [[tool.mypy.overrides]] to disable arg-type in
  sqlmodel_repo.*: pydantic plugin resolves .where(Model.field == v) as
  where(bool), a false positive; call-arg still catches real argument errors
- Remove 9 stale # type: ignore comments (logging, helpers, credentials)
- Fix telemetry.py traced() overload no-redef + misc
- Fix logs.py datetime/str operator and nullable PK comparison with col()
- sqlmodel_repo/ now has 0 mypy errors

decnet/telemetry.py

@@ -138,7 +138,7 @@ def traced(fn: F) -> F: ...
 def traced(name: str) -> Callable[[F], F]: ...
 
 
-def traced(fn: Any = None, *, name: str | None = None) -> Any:
+def traced(fn: Any = None, *, name: str | None = None) -> Any:  # type: ignore[misc]
     """Decorator that wraps a function in an OTEL span.
 
     Usage::
@@ -168,9 +168,9 @@ def traced(fn: Any = None, *, name: str | None = None) -> Any:
         # Called as @traced (no arguments)
         return _wrap(fn, None)
     # Fallback: @traced() with no args
-    def decorator(f: F) -> F:
+    def _fallback_decorator(f: F) -> F:
         return _wrap(f, name)
-    return decorator
+    return _fallback_decorator
 
 
 def _wrap(fn: F, span_name: str | None) -> F: