fix: use Bun.file().text() at module scope to inline test-api.html

Bun HTML import returns HTMLBundle object on Vercel serverless, which
renders as '[object HTMLBundle]'. Using Bun.file().text() at top-level
module scope ensures Bun bundler inlines the raw string at build time.

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

api/relay.ts

@@ -29,7 +29,10 @@ import { createRateLimiter } from "../src/middleware/rate-limiter";
 import { logRelayEvent } from "../src/middleware/logger";
 import { handleChatCompletion, listModels } from "../src/lib/ai-proxy";
 import { handleAnthropicMessages } from "../src/lib/anthropic-proxy";
-import testApiHtml from "../public/test-api.html" with { type: "text" };
+
+// Read test-api.html at module scope so Bun's bundler inlines the content
+// at build time (Vercel serverless has no filesystem at runtime).
+const testApiHtmlRaw = await Bun.file("public/test-api.html").text();
 
 // ─── Configuration ──────────────────────────────────────────────────────────────
 
@@ -382,7 +385,7 @@ export default {
 		// Static routes — show index only when no relay target is requested
 		if (url.pathname === "/health") return handleHealth();
 		if (url.pathname === "/docs" || url.pathname === "/test") {
-			return new Response(testApiHtml, {
+			return new Response(testApiHtmlRaw, {
 				headers: { "Content-Type": "text/html; charset=utf-8" },
 			});
 		}