Fix parameter path indexing and add PostCSS configuration

- Fix federal bracket rates to use 1-indexed keys (range(1,8)) matching YAML
- Add .amount sub-key to EITC max bracket scale paths
- Add .rate sub-key to VA income tax rate bracket scale paths
- Add postcss.config.mjs with @tailwindcss/postcss plugin (required for Tailwind v4)
- Add @tailwindcss/postcss and postcss as devDependencies

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

Author: anth-volk

backend/simulation.py

@@ -77,9 +77,9 @@ class StatewideImpactRequest(BaseModel):
     "head_of_household": "HEAD_OF_HOUSEHOLD",
 }
 
-# Federal income tax bracket rate parameter paths (7 brackets, 1-indexed)
+# Federal income tax bracket rate parameter paths (7 brackets, 1-indexed keys in YAML)
 FEDERAL_BRACKET_RATE_PATHS = [
-    f"gov.irs.income.bracket.rates[{i}]" for i in range(7)
+    f"gov.irs.income.bracket.rates[{i}]" for i in range(1, 8)
 ]
 
 # Federal CTC parameter paths
@@ -88,14 +88,14 @@ class StatewideImpactRequest(BaseModel):
 FEDERAL_CTC_REFUNDABLE_MAX_PATH = "gov.irs.credits.ctc.refundable.individual_max"
 FEDERAL_CTC_FULLY_REFUNDABLE_PATH = "gov.irs.credits.ctc.refundable.fully_refundable"
 
-# Federal EITC max parameter paths (indexed by number of children: 0, 1, 2, 3)
+# Federal EITC max parameter paths (bracket scale, 0-indexed, needs .amount sub-key)
 FEDERAL_EITC_MAX_PATHS = [
-    f"gov.irs.credits.eitc.max[{i}]" for i in range(4)
+    f"gov.irs.credits.eitc.max[{i}].amount" for i in range(4)
 ]
 
-# Virginia income tax rate parameter paths (4 brackets, 0-indexed)
+# Virginia income tax rate parameter paths (bracket scale, 0-indexed, needs .rate sub-key)
 VA_RATE_PATHS = [
-    f"gov.states.va.tax.income.rates[{i}]" for i in range(4)
+    f"gov.states.va.tax.income.rates[{i}].rate" for i in range(4)
 ]
 
 # Virginia standard deduction

package.json

@@ -18,13 +18,15 @@
     "tailwindcss": "^4"
   },
   "devDependencies": {
+    "@tailwindcss/postcss": "^4.2.1",
     "@testing-library/jest-dom": "^6",
     "@testing-library/react": "^16",
     "@types/node": "^22",
     "@types/react": "^19",
     "@types/react-dom": "^19",
     "@vitejs/plugin-react": "4.3.4",
     "jsdom": "^25",
+    "postcss": "^8.5.8",
     "typescript": "^5",
     "vitest": "^2"
   }

postcss.config.mjs

@@ -0,0 +1,5 @@
+export default {
+  plugins: {
+    "@tailwindcss/postcss": {},
+  },
+};