Usage: add cost summaries to /usage + mac menu

src/gateway/server-methods/usage.ts

@@ -1,3 +1,5 @@
+import { loadConfig } from "../../config/config.js";
+import { loadCostUsageSummary } from "../../infra/session-cost-usage.js";
 import { loadProviderUsageSummary } from "../../infra/provider-usage.js";
 import type { GatewayRequestHandlers } from "./types.js";
 
@@ -6,4 +8,9 @@ export const usageHandlers: GatewayRequestHandlers = {
     const summary = await loadProviderUsageSummary();
     respond(true, summary, undefined);
   },
+  "usage.cost": async ({ respond }) => {
+    const config = loadConfig();
+    const summary = await loadCostUsageSummary({ days: 30, config });
+    respond(true, summary, undefined);
+  },
 };