Goal/rubric state channels shared by every schema that touches them.
Declared once here so each schema that carries these channels —
ResumeState and goal_tools.GoalToolState — inherits the same
PrivateStateAttr-marked annotations. Middleware state schemas merge with
later entries winning, so an independent re-declaration that dropped the
PrivateStateAttr marker would override these and leak the field into the
public graph input/output schema. Inheriting from a single base makes that
drift unrepresentable.
