feat(billing): make metering formula admin-configurable

Allow margin/FX/cost-mode knobs to be overridden via h5_billing_admin_config so memind_adm can adjust DeepSeek billing without editing env.

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

billing-token-state.mjs

@@ -35,7 +35,7 @@ export function estimateAccumulatedCostUsd(tokenStateRaw, estimateConfig = loadC
 
 export function enrichTokenStateForBilling(
   tokenStateRaw,
-  { sessionCost = null } = {},
+  { sessionCost = null, estimateConfig = null } = {},
   env = process.env,
 ) {
   const state = normalizeTokenState(tokenStateRaw);
@@ -49,7 +49,10 @@ export function enrichTokenStateForBilling(
     return state;
   }
 
-  const estimatedUsd = estimateAccumulatedCostUsd(state, loadCostEstimateConfig(env));
+  const estimatedUsd = estimateAccumulatedCostUsd(
+    state,
+    estimateConfig ?? loadCostEstimateConfig(env),
+  );
   if (estimatedUsd != null) {
     return { ...state, accumulatedCost: estimatedUsd };
   }
@@ -86,7 +89,13 @@ async function resolveSessionCostPayload(sessionId, fetchSession, fetchSessionCo
 
 export async function resolveBillingTokenState(
   tokenStateRaw,
-  { sessionId = null, fetchSession = null, fetchSessionCostFromPg = null } = {},
+  {
+    sessionId = null,
+    fetchSession = null,
+    fetchSessionCostFromPg = null,
+    estimateConfig = null,
+    loadEstimateConfig = null,
+  } = {},
   env = process.env,
 ) {
   const state = normalizeTokenState(tokenStateRaw);
@@ -96,5 +105,9 @@ export async function resolveBillingTokenState(
     fetchSessionCostFromPg,
     env,
   );
-  return enrichTokenStateForBilling(state, { sessionCost }, env);
+  const resolvedEstimateConfig =
+    estimateConfig
+    ?? (typeof loadEstimateConfig === 'function' ? await loadEstimateConfig() : null)
+    ?? loadCostEstimateConfig(env);
+  return enrichTokenStateForBilling(state, { sessionCost, estimateConfig: resolvedEstimateConfig }, env);
 }