Add modal sandbox support (#192)

* add modal sandbox example

* add test instructions

---------

Co-authored-by: Nathan Flurry <NathanFlurry@users.noreply.github.com>

examples/modal/tests/modal.test.ts

@@ -0,0 +1,28 @@
+import { describe, it, expect } from "vitest";
+import { buildHeaders } from "@sandbox-agent/example-shared";
+import { setupModalSandboxAgent } from "../src/modal.ts";
+
+const shouldRun = Boolean(process.env.MODAL_TOKEN_ID && process.env.MODAL_TOKEN_SECRET);
+const timeoutMs = Number.parseInt(process.env.SANDBOX_TEST_TIMEOUT_MS || "", 10) || 300_000;
+
+const testFn = shouldRun ? it : it.skip;
+
+describe("modal example", () => {
+  testFn(
+    "starts sandbox-agent and responds to /v1/health",
+    async () => {
+      const { baseUrl, cleanup } = await setupModalSandboxAgent();
+      try {
+        const response = await fetch(`${baseUrl}/v1/health`, {
+          headers: buildHeaders({}),
+        });
+        expect(response.ok).toBe(true);
+        const data = await response.json();
+        expect(data.status).toBe("ok");
+      } finally {
+        await cleanup();
+      }
+    },
+    timeoutMs,
+  );
+});