Implement Montana State Supplementary Payment (SSP)

[hua7450]

Goal

Implement Montana's State Supplementary Payment (SSP) — Montana's supplement to federal Supplemental Security Income (SSI).

Scope

• Add Montana SSP parameters under parameters/gov/states/mt/
• Add Montana SSP variables under variables/gov/states/mt/
• Add YAML tests under tests/policy/baseline/gov/states/mt/
• Register the program in programs.yaml
• Wire the SSP payment into household state benefits (spm_unit_benefits.py, household_state_benefits.yaml)

Regulatory Authority

To be confirmed during implementation (Montana DPHHS / state statutes / SSA SSI State Factsheets).

Notes

• Eligibility typically requires receipt of federal SSI (ssi > 0) plus state residency.
• Verify benefit amounts and any categorical distinctions (aged/blind/disabled, living arrangement, couple treatment) against primary sources.