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/web/db/sqlmodel_repo/webhooks.py

@@ -5,11 +5,14 @@ from datetime import datetime, timezone
 from typing import Any, Optional
 
 from sqlalchemy import select, update
+from sqlmodel import col
 
 from decnet.web.db.models import WebhookSubscription
 
 
-class WebhooksMixin:
+from decnet.web.db.sqlmodel_repo._helpers import _MixinBase
+
+class WebhooksMixin(_MixinBase):
     """Mixin: composed onto ``SQLModelRepository``."""
 
     async def create_webhook_subscription(self, data: dict[str, Any]) -> None:
@@ -43,7 +46,7 @@ class WebhooksMixin:
         async with self._session() as session:
             stmt = select(WebhookSubscription)
             if enabled_only:
-                stmt = stmt.where(WebhookSubscription.enabled.is_(True))
+                stmt = stmt.where(col(WebhookSubscription.enabled).is_(True))
             stmt = stmt.order_by(WebhookSubscription.created_at)
             result = await session.execute(stmt)
             return [r.model_dump() for r in result.scalars().all()]
@@ -100,7 +103,7 @@ class WebhooksMixin:
             # the counter informs the circuit-breaker heuristic, not a
             # correctness invariant.
             result = await session.execute(
-                select(WebhookSubscription.consecutive_failures).where(
+                select(col(WebhookSubscription.consecutive_failures)).where(
                     WebhookSubscription.uuid == uuid
                 )
             )