feat(rpc): add the caller-side example and close remaining coverage gaps

Adds examples/auth-showcase/app/services/greeter-client.ts so the showcase
demonstrates both halves - the review noted the example was callee-only, so a
developer had no working reference for making a call.

Raises integration coverage to the planned 3 tests and adds the missing
rpc-endpoint cases. Also wires the prod build path for services.

304 tests pass across rpc/router/dev-server/cli; typecheck, lint, format and
check:public-api all clean.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

packages/dev-server/test/rpc-endpoint.test.ts

@@ -2,6 +2,7 @@ import { describe, expect, test } from "bun:test";
 import { defineService, implement, procedure } from "@wrnexus/rpc";
 import { v } from "@wrnexus/validation";
 import { handleRpcRequest, isInternalCaller, isRpcPath } from "../src/rpc-dispatch.ts";
+import { createProductionHandlers, type ProdManifest } from "../src/prod.ts";
 
 const demo = defineService({
   name: "demo",
@@ -73,4 +74,20 @@ describe("RPC endpoint", () => {
       expect(await res!.json()).toMatchObject({ ok: false, code: "RPC_UNKNOWN" });
     });
   });
+
+  test("production manifests load and dispatch service implementations", async () => {
+    const manifest: ProdManifest = {
+      pages: [],
+      api: [],
+      realtime: [],
+      middleware: [],
+      components: [],
+      layouts: [],
+      services: [{ name: "demo", mod: { default: services.get("demo") } }],
+    };
+    const handlers = createProductionHandlers(manifest, {});
+    const req = request("/__wrnexus/rpc/demo/add", { "x-wrnexus-internal": "1" });
+    const response = await handlers.fetch(req, {} as never);
+    expect(await response!.json()).toEqual({ ok: true, value: { a: 2 } });
+  });
 });