feat(grok): improve free quota probing and usage

frontend/src/types/index.ts

@@ -1020,10 +1020,38 @@ export interface AntigravityModelQuota {
 }
 
 export interface GrokQuotaWindow {
-  limit?: number
-  remaining?: number
-  reset_unix?: number
-  reset_at?: string
+  limit?: number | null
+  remaining?: number | null
+  reset_unix?: number | null
+  reset_at?: string | null
+}
+
+export interface GrokBillingProductUsage {
+  product: string
+  usage_percent?: number | null
+}
+
+export interface GrokBillingSummary {
+  period_type?: string
+  usage_percent?: number | null
+  period_start?: string
+  period_end?: string
+  product_usage?: GrokBillingProductUsage[]
+  monthly_limit_cents?: number | null
+  used_cents?: number | null
+  included_used_cents?: number | null
+  billing_period_start?: string
+  billing_period_end?: string
+  used_percent?: number | null
+  plan?: string
+  status_code?: number
+  source?: string
+  fetched_at?: string
+  updated_at?: string
+  weekly_updated_at?: string
+  monthly_updated_at?: string
+  partial?: boolean
+  failed_windows?: string[]
 }
 
 export interface AccountUsageInfo {
@@ -1049,6 +1077,11 @@ export interface AccountUsageInfo {
   grok_last_headers_seen_at?: string
   grok_last_status_code?: number
   grok_local_usage?: WindowStats | null
+  grok_local_usage_7d?: WindowStats | null
+  grok_local_usage_monthly?: WindowStats | null
+  grok_billing?: GrokBillingSummary | null
+  subscription_tier?: string
+  subscription_tier_raw?: string
   ai_credits?: Array<{
     credit_type?: string
     amount?: number