fix: update v2 session usage metrics (#35468)

packages/tui/src/util/session.ts

@@ -1,3 +1,17 @@
+import type { SessionMessage, SessionMessageAssistant } from "@opencode-ai/sdk/v2"
+
 export function isDefaultTitle(title: string) {
   return /^(New session - |Child session - )\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}\.\d{3}Z$/.test(title)
 }
+
+export function lastAssistantWithUsage(messages: ReadonlyArray<SessionMessage>, boundary?: string) {
+  const boundaryIndex = boundary ? messages.findIndex((message) => message.id === boundary) : -1
+  if (boundary && boundaryIndex === -1) return undefined
+  return messages.findLast(
+    (
+      message,
+      index,
+    ): message is SessionMessageAssistant & { tokens: NonNullable<SessionMessageAssistant["tokens"]> } =>
+      message.type === "assistant" && message.tokens !== undefined && (boundaryIndex === -1 || index < boundaryIndex),
+  )
+}