fix(invariants): address review feedback for PR #11037

- Fix Ruff E303: reduce blank lines before InvariantModel to 2 (models.py)
- Add type ignore on behave.runner import (invariant_model_steps.py)
- Add CheckConstraint('description != ''') on InvariantModel and migration
- Fix migration chain: update down_revision to reference latest head m9_003

Also removes deleted file stdio_transport.py that was part of merged-in PR changes.

Addresses review items #1, #2, #6, #8 from HAL9001.

features/steps/invariant_model_steps.py

@@ -10,7 +10,7 @@ import uuid
 from datetime import UTC, datetime
 
 from behave import given, then, when  # type: ignore[import-untyped]
-from behave.runner import Context
+from behave.runner import Context  # type: ignore[import-untyped]
 from sqlalchemy import create_engine, inspect
 from sqlalchemy.orm import sessionmaker
 

src/cleveragents/infrastructure/database/migrations/versions/m3_001_invariants_table.py

@@ -35,6 +35,7 @@ def upgrade() -> None:
             server_default=sa.text("1"),
         ),
         sa.PrimaryKeyConstraint("id"),
+        sa.CheckConstraint("description != ''"),
     )
     op.create_index("ix_invariants_is_active", "invariants", ["is_active"])
 

src/cleveragents/infrastructure/database/migrations/versions/m3_002_merge_invariants_and_a5_006.py

@@ -2,7 +2,8 @@
 
 This merge migration resolves the two-head situation created when
 m3_001_invariants_table and a5_006_action_invariants_unique_constraint
-both branched from m9_002_plan_resume_fields.
+both branched from m9_002_plan_resume_fields, with the a5_006 chain
+further progressing through to m9_003_plan_result_success_column.
 
 Revision ID: m3_002_merge_invariants_and_a5_006
 Revises: m3_001_invariants_table, a5_006_action_invariants_unique_constraint
@@ -15,7 +16,7 @@ from collections.abc import Sequence
 revision: str = "m3_002_merge_invariants_and_a5_006"
 down_revision: str | Sequence[str] | None = (
     "m3_001_invariants_table",
-    "a5_006_action_invariants_unique_constraint",
+    "m9_003_plan_result_success_column",
 )
 branch_labels: str | Sequence[str] | None = None
 depends_on: str | Sequence[str] | None = None

src/cleveragents/infrastructure/database/models.py

@@ -1311,7 +1311,6 @@ class PlanInvariantModel(Base):  # type: ignore[misc]
     )
 
 
-
 class InvariantModel(Base):  # type: ignore[misc]
     """SQLAlchemy database model for global invariants.
 
@@ -1335,6 +1334,8 @@ class InvariantModel(Base):  # type: ignore[misc]
         server_default=text("1"),
     )
 
+    __table_args__ = (CheckConstraint("description != ''"),)
+
     def __repr__(self) -> str:
         return (
             f"InvariantModel(id={self.id!r}, "