Upgrade API v1 to PolicyEngine.py 6.2.1 #3867

Objective

Upgrade API v1 to the PolicyEngine.py 6.2.1 model bundle and verify that the API and simulation service use compatible package and Supplemental Poverty Measure configurations.

Scope

• Install policyengine[models]==6.2.1.
• Use the bundle-selected PolicyEngine Core 3.32.10, PolicyEngine US 2.2.1, PolicyEngine UK 2.102.3, and spm-calculator 1.0.0 releases.
• Update API fixtures and expected model-catalog values for the new bundle.
• Validate that the simulation service exposes the same PolicyEngine.py, US, UK, and SPM configuration before dependent API validation and deployment jobs proceed.
• Update the automated PolicyEngine.py dependency workflow to modify and validate the complete bundle atomically.
• Document the installed package and certified dataset versions.

Integration

The corresponding simulation-service support was delivered through PolicyEngine/policyengine-sim-api#703. The API implementation is included in #3855.