fix(billing): prefer Goose session cost over token estimate

Billing fell back to inflated token list-price estimates when Finish
frames carried inline accumulatedCost, causing ~70x overcharge vs DeepSeek.
Always fetch session accumulated_cost first; add Aug 4+ compensation script.

Co-authored-by: Cursor <cursoragent@cursor.com>

billing-token-state.mjs

@@ -38,15 +38,16 @@ export function enrichTokenStateForBilling(
   env = process.env,
 ) {
   const state = normalizeTokenState(tokenStateRaw);
-  if (state.accumulatedCost != null && Number(state.accumulatedCost) >= 0) {
-    return state;
-  }
 
   const sessionUsd = pickSessionAccumulatedCost(sessionCost);
   if (sessionUsd != null) {
     return { ...state, accumulatedCost: sessionUsd };
   }
 
+  if (state.accumulatedCost != null && Number(state.accumulatedCost) >= 0) {
+    return state;
+  }
+
   const estimatedUsd = estimateAccumulatedCostUsd(state, loadCostEstimateConfig(env));
   if (estimatedUsd != null) {
     return { ...state, accumulatedCost: estimatedUsd };
@@ -61,9 +62,6 @@ export async function resolveBillingTokenState(
   env = process.env,
 ) {
   const state = normalizeTokenState(tokenStateRaw);
-  if (state.accumulatedCost != null && Number(state.accumulatedCost) >= 0) {
-    return state;
-  }
 
   if (typeof fetchSession === 'function' && sessionId) {
     try {
@@ -71,7 +69,7 @@ export async function resolveBillingTokenState(
       const enriched = enrichTokenStateForBilling(state, { sessionCost: session }, env);
       if (enriched.accumulatedCost != null) return enriched;
     } catch {
-      // Best-effort: fall through to token estimate.
+      // Best-effort: fall through to inline cost / token estimate.
     }
   }