fix: query TaxBenefitModel by name before getting version (#69)

* feat: add structural reform support for economy and household calculations

Adds run_structural_reform tool for the agent to run economy-wide structural reforms:
- Agent calls POST /agent/run-structural-reform to trigger Modal
- Modal applies simulation_modifier to reform simulation
- Decile impacts calculated and stored
- Agent polls until completion

Also adds simulation_modifier support to household calculations:
- Updated Modal household functions to use low-level Simulation API when modifier present
- Added helper functions _calculate_uk/us_household_with_modifier
- Updated _get_policy_data to include simulation_modifier
- Agent can use policy_id with modifier in /household/calculate

Fixes broken policyengine.outputs.inequality/poverty imports (module doesn't exist yet).

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* fix: query TaxBenefitModel by name before getting version

TaxBenefitModelVersion doesn't have a name field - need to query
TaxBenefitModel first, then get the version by model_id.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: nikhilwoodruff

src/policyengine_api/api/agent_results.py

@@ -25,6 +25,7 @@
     ReportStatus,
     Simulation,
     SimulationStatus,
+    TaxBenefitModel,
     TaxBenefitModelVersion,
     Dataset,
 )
@@ -446,8 +447,17 @@ def run_structural_reform(
     )
     from sqlmodel import select
 
+    # First find the model by name, then get its latest version
+    stmt = select(TaxBenefitModel).where(TaxBenefitModel.name == tax_benefit_model_name)
+    model = session.exec(stmt).first()
+    if not model:
+        raise HTTPException(
+            status_code=404,
+            detail=f"No model found for {tax_benefit_model_name}",
+        )
+
     stmt = select(TaxBenefitModelVersion).where(
-        TaxBenefitModelVersion.name == tax_benefit_model_name
+        TaxBenefitModelVersion.model_id == model.id
     )
     model_version = session.exec(stmt).first()
     if not model_version: