feat(redstone): /ai_use — OpenRouter key usage report

Admin-only command. Calls GET https://openrouter.ai/api/v1/key (the
REST equivalent of the @openrouter/sdk's apiKeys.getCurrent()) and
formats the result:

- active model (from the settings table)
- tier (🟢 free / 💰 paid)
- credit limit + remaining (or "none")
- credits spent today / week / month / all-time

Plus a note that free-model requests don't draw credits — they're
capped separately at 50/day (UTC-midnight reset), liftable to
1000/day with $10 credit. Kept fetch-based like the rest of the
OpenRouter integration rather than pulling in the SDK.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

bot/bot.ts

@@ -626,6 +626,62 @@ async function fetchOpenRouterModels(): Promise<ORModelListItem[]> {
   return data.data ?? [];
 }
 
+// OpenRouter key/usage info — GET /api/v1/key (equivalent to the SDK's
+// openRouter.apiKeys.getCurrent()). Surfaces credit usage + tier.
+type ORKeyInfo = {
+  label?: string;
+  is_free_tier?: boolean;
+  limit?: number | null;
+  limit_remaining?: number | null;
+  usage?: number;
+  usage_daily?: number;
+  usage_weekly?: number;
+  usage_monthly?: number;
+};
+
+async function fetchOpenRouterKeyInfo(): Promise<ORKeyInfo> {
+  if (!OPENROUTER_API_KEY) throw new Error("OPENROUTER_API_KEY not configured");
+  const res = await fetch("https://openrouter.ai/api/v1/key", {
+    headers: { Authorization: `Bearer ${OPENROUTER_API_KEY}`, Accept: "application/json" },
+    signal: AbortSignal.timeout(15_000),
+  });
+  if (!res.ok) throw new Error(`openrouter /key -> ${res.status}`);
+  const data = (await res.json()) as { data?: ORKeyInfo };
+  return data.data ?? {};
+}
+
+async function renderAiUsage(ctx: Context) {
+  if (!OPENROUTER_API_KEY) {
+    await sendText(ctx, "OpenRouter is not configured — set OPENROUTER_API_KEY to see usage.");
+    return;
+  }
+  let info: ORKeyInfo;
+  try {
+    info = await fetchOpenRouterKeyInfo();
+  } catch (e) {
+    await sendText(ctx, `Couldn't load OpenRouter usage: ${escape((e as Error).message)}`);
+    return;
+  }
+  const usd = (n: number | null | undefined) =>
+    n == null ? "—" : `$${n.toFixed(n < 1 ? 4 : 2)}`;
+  const tier = info.is_free_tier ? "🟢 free tier" : "💰 paid";
+  const limitLine = info.limit == null
+    ? "Credit limit: <i>none</i>"
+    : `Credit limit: ${usd(info.limit)} (remaining ${usd(info.limit_remaining)})`;
+  const text =
+    `<b>🤖 OpenRouter usage</b>\n\n` +
+    `Active model: <code>${escape(currentOpenRouterModel())}</code>\n` +
+    `Tier: ${tier}\n` +
+    `${limitLine}\n\n` +
+    `<b>Credits spent</b>\n` +
+    `• today: ${usd(info.usage_daily)}\n` +
+    `• this week: ${usd(info.usage_weekly)}\n` +
+    `• this month: ${usd(info.usage_monthly)}\n` +
+    `• all time: ${usd(info.usage)}\n\n` +
+    `<i>Free-model requests don't consume credits — they're capped separately at 50/day, resetting at UTC midnight. Add $10 of credit to lift that to 1000/day.</i>`;
+  await sendText(ctx, text);
+}
+
 function modelButtonLabel(m: ORModelListItem, isCurrent: boolean): string {
   const free = isFreeModel(m);
   const thinking = m.supported_parameters?.includes("reasoning") ?? false;
@@ -1104,6 +1160,9 @@ bot.command("teststicker", admin(async (ctx) => {
 // is resolved at every callOpenRouterOnce so changes apply immediately.
 bot.command("model", admin(async (ctx) => { await renderModelPicker(ctx); }));
 
+// OpenRouter usage — admin views credit spend + tier for the configured key.
+bot.command("ai_use", admin(async (ctx) => { await renderAiUsage(ctx); }));
+
 // History — last N messages in this chat
 bot.command("history", admin(async (ctx) => {
   const n = Math.min(50, Math.max(5, Number.parseInt((ctx.match as string).trim(), 10) || 20));