test(runtime-ts): pin literal META_CONTENT_TYPE value to catch constant typos

Add independent literal assertion in the Fastify test to detect changes to
the constant's value itself. Hono test asserts against the constant only,
proving the mount references it. Together: mounts agree, and the constant
itself is correct.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015NrWUxA6euwvnFcwKxcK6A

Author: dmealing

server/typescript/packages/runtime-ts/test/meta-route.test.ts

@@ -16,6 +16,10 @@ describe("GET /_meta (fastify)", () => {
     const res = await app.inject({ method: "GET", url: "/api/_meta" });
 
     expect(res.statusCode).toBe(200);
+    // Pinned independently of META_CONTENT_TYPE: asserting only against the constant
+    // the mounts also use proves the two mounts AGREE, but cannot catch the constant
+    // itself being wrong. One literal here closes that loop.
+    expect(META_CONTENT_TYPE).toBe("application/json; charset=utf-8");
     expect(res.headers["content-type"]).toBe(META_CONTENT_TYPE);
     expect(res.body).toBe(metaJson(root));
   });