feat(chat): add local-first conversation workspace

chat/lib/response-metadata.ts

@@ -1,10 +1,24 @@
 import type {ResponseMetadata} from "./conversation-types";
 
-export function responseMetadata(providerId: string, model: string, startedAt: number, outputTokens: number | undefined | null): ResponseMetadata {
+function normalizeTokenCount(value: unknown): number | null {
+  if (typeof value === "number" && Number.isFinite(value) && value >= 0) return Math.round(value);
+  if (typeof value === "bigint" && value >= 0n) return Number(value);
+  if (typeof value === "string") {
+    const parsed = Number(value);
+    if (Number.isFinite(parsed) && parsed >= 0) return Math.round(parsed);
+  }
+  return null;
+}
+
+export function responseMetadata(
+  providerId: string,
+  model: string,
+  startedAt: number,
+  outputTokens: number | undefined | null,
+  fallbackOutputTokens?: number | undefined | null
+): ResponseMetadata {
   const durationMs = Math.max(1, Math.round(performance.now() - startedAt));
-  const normalizedTokens = typeof outputTokens === "number" && Number.isFinite(outputTokens) && outputTokens >= 0
-    ? Math.round(outputTokens)
-    : null;
+  const normalizedTokens = normalizeTokenCount(outputTokens) ?? normalizeTokenCount(fallbackOutputTokens);
   const tokensPerSecond = normalizedTokens === null
     ? null
     : Math.round((normalizedTokens / (durationMs / 1000)) * 10) / 10;