Break CO CCAP → snap_fpg circular dependency via spm_unit_fpg

CO CCAP used snap_fpg for its FPG calculation, creating a cycle:
tanf → childcare_expenses → co_ccap_subsidy → co_ccap_fpg_eligible
→ snap_fpg → snap_unit_size → is_snap_ineligible_student
→ tanf_person → tanf

Replaced with spm_unit_fpg (existing HHS FPG variable using
spm_unit_size) divided by 12 for monthly values. No new variable
needed — reuses the existing annual FPG with time-based indexing.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: MaxGhenis

policyengine_us/tests/policy/baseline/gov/states/co/ccap/co_ccap_add_on_parent_fee.yaml

@@ -3,7 +3,7 @@
   input:
     co_ccap_eligible_children: 1
     co_ccap_countable_income: 60_000
-    snap_fpg: 120_000
+    spm_unit_fpg: 120_000
   output:
     co_ccap_add_on_parent_fee: 
       2023-01: 0
@@ -13,7 +13,7 @@
   input:
     co_ccap_eligible_children: 1
     co_ccap_countable_income: 80_000
-    snap_fpg: 40_000
+    spm_unit_fpg: 40_000
   output:
     co_ccap_add_on_parent_fee: 
       2023-01: 0
@@ -23,7 +23,7 @@
   input:
     co_ccap_eligible_children: 2
     co_ccap_countable_income: 60_000
-    snap_fpg: 120_000
+    spm_unit_fpg: 120_000
   output:
     co_ccap_add_on_parent_fee: 
       2023-01: 0
@@ -33,7 +33,7 @@
   input:
     co_ccap_eligible_children: 2
     co_ccap_countable_income: 80_000
-    snap_fpg: 40_000
+    spm_unit_fpg: 40_000
   output:
     co_ccap_add_on_parent_fee: 
       2023-01: 15
@@ -43,7 +43,7 @@
   input:
     co_ccap_eligible_children: 1
     co_ccap_countable_income: 60_000
-    snap_fpg: 120_000
+    spm_unit_fpg: 120_000
   output:
     co_ccap_add_on_parent_fee: 
       2022-12: 0
@@ -53,7 +53,7 @@
   input:
     co_ccap_eligible_children: 1
     co_ccap_countable_income: 80_000
-    snap_fpg: 40_000
+    spm_unit_fpg: 40_000
   output:
     co_ccap_add_on_parent_fee: 
       2022-12: 0
@@ -63,7 +63,7 @@
   input:
     co_ccap_eligible_children: 2
     co_ccap_countable_income: 60_000
-    snap_fpg: 120_000
+    spm_unit_fpg: 120_000
   output:
     co_ccap_add_on_parent_fee: 
       2022-12: 0
@@ -73,7 +73,7 @@
   input:
     co_ccap_eligible_children: 2
     co_ccap_countable_income: 80_000
-    snap_fpg: 40_000
+    spm_unit_fpg: 40_000
   output:
     co_ccap_add_on_parent_fee: 
       2022-12: 15

policyengine_us/tests/policy/baseline/gov/states/co/ccap/co_ccap_base_parent_fee.yaml

@@ -2,7 +2,7 @@
   period: 2023
   input:
     co_ccap_countable_income: 60_000
-    snap_fpg: 120_000
+    spm_unit_fpg: 120_000
     state_code: CO
   output:
     co_ccap_base_parent_fee: 
@@ -12,7 +12,7 @@
   period: 2023
   input:
     co_ccap_countable_income: 80_000
-    snap_fpg: 40_000
+    spm_unit_fpg: 40_000
     state_code: CO
   output:
     co_ccap_base_parent_fee: 
@@ -22,7 +22,7 @@
   period: 2022
   input:
     co_ccap_countable_income: 60_000
-    snap_fpg: 120_000
+    spm_unit_fpg: 120_000
     state_code: CO
   output:
     co_ccap_base_parent_fee: 
@@ -32,7 +32,7 @@
   period: 2022
   input:
     co_ccap_countable_income: 80_000
-    snap_fpg: 40_000
+    spm_unit_fpg: 40_000
     state_code: CO
   output:
     co_ccap_base_parent_fee: 

policyengine_us/tests/policy/baseline/gov/states/co/ccap/entry/co_ccap_fpg_eligible.yaml

@@ -4,7 +4,7 @@
     state_code_str: CO
     co_ccap_countable_income: 2.3
     county_str: ADAMS_COUNTY_CO
-    snap_fpg: 1
+    spm_unit_fpg: 12
   output:
     co_ccap_fpg_eligible: true
 
@@ -14,7 +14,7 @@
     state_code_str: CO
     co_ccap_countable_income: 2.3
     county_str: BACA_COUNTY_CO
-    snap_fpg: 1
+    spm_unit_fpg: 12
   output:
     co_ccap_fpg_eligible: false
 
@@ -24,6 +24,6 @@
     state_code_str: MN
     co_ccap_countable_income: 0
     county_str: HENNEPIN_COUNTY_MN
-    snap_fpg: 1
+    spm_unit_fpg: 12
   output:
     co_ccap_fpg_eligible: false

policyengine_us/variables/gov/states/co/ccap/co_ccap_add_on_parent_fee.py

@@ -21,8 +21,7 @@ def formula(spm_unit, period, parameters):
         p = parameters(instant_str).gov.states.co.ccap
         # Calculate base parent fee and add on parent fee.
         gross_income = spm_unit("co_ccap_countable_income", period)
-        # snap_fpg is monthly.
-        snap_fpg = spm_unit("snap_fpg", period)
+        fpg = spm_unit("spm_unit_fpg", period.this_year) / MONTHS_IN_YEAR
         eligible_children = spm_unit("co_ccap_eligible_children", period)
         # Calculate add-on parent fee based on the number of eligible
         # children in a household and income:
@@ -31,5 +30,5 @@ def formula(spm_unit, period, parameters):
         add_on_parent_fee_amount = (
             eligible_children - 1
         ) * p.parent_fee.add_on
-        add_on_parent_fee_applies = gross_income > snap_fpg
+        add_on_parent_fee_applies = gross_income > fpg
         return add_on_parent_fee_amount * add_on_parent_fee_applies

policyengine_us/variables/gov/states/co/ccap/co_ccap_base_parent_fee.py

@@ -21,12 +21,11 @@ def formula(spm_unit, period, parameters):
         p = parameters(instant_str).gov.states.co.ccap
         # Calculate base parent fee and add on parent fee.
         gross_income = spm_unit("co_ccap_countable_income", period)
-        # snap_fpg is monthly.
-        snap_fpg = spm_unit("snap_fpg", period)
+        fpg = spm_unit("spm_unit_fpg", period.this_year) / MONTHS_IN_YEAR
         # Calculate base parent fee scaled (note income is monthly):
         # When income_scaled <= 1: income_scaled * 0.01
         # When income_scaled > 1: [1 * 0.01 + (income_scaled - 1) * 0.14]
         # Multiply by fpg afterward to scale back up
-        gross_income_fpg_ratio = gross_income / snap_fpg
+        gross_income_fpg_ratio = gross_income / fpg
         base_parent_fee_scaled = p.parent_fee.base.calc(gross_income_fpg_ratio)
-        return base_parent_fee_scaled * snap_fpg
+        return base_parent_fee_scaled * fpg

policyengine_us/variables/gov/states/co/ccap/entry/co_ccap_fpg_eligible.py

@@ -36,8 +36,7 @@ def formula(spm_unit, period, parameters):
             )
         if mask.any():
             fpg_rate[mask] = p.entry.fpg_rate[county[mask]]
-        # SNAP FPG is monthly.
-        fpg = spm_unit("snap_fpg", period)
+        fpg = spm_unit("spm_unit_fpg", period.this_year) / MONTHS_IN_YEAR
         fpg_limit = np.round(fpg * fpg_rate, 2)
         meets_income_limit = monthly_gross_income < fpg_limit
         return state_eligible & meets_income_limit