feat(rpc): transport, server, client, http, mounting, docs (Tasks 5-11)

Brings the uncommitted body of work under version control so it cannot be
lost. Gates are green: 152 tests pass across rpc/router/dev-server,
typecheck, lint, format and check:public-api all clean.

NOT YET REVIEWED. None of Tasks 5-11 has had an independent task review, and
Task 4's second fix round was never re-reviewed either.

Known gaps against the plan, recorded here rather than discovered later:
- packages/rpc/test/{transport,server,client}.test.ts are ABSENT. The plan
  required a test file for each. server.ts holds the fail-closed identity and
  permission checks and currently has no direct coverage at all.
- rpc-endpoint.test.ts has 3 tests where the plan specified 9. Missing:
  unknown service, non-POST, malformed body, non-rpc passthrough, and the
  isInternalCaller sweep. This is the task where a reachable
  /__wrnexus/rpc/* makes every permission check in the workspace bypassable.
- http.test.ts has 3 of 7; integration.test.ts 2 of 3;
  services-discovery.test.ts 1 of 4.

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

examples/auth-showcase/app/services/greeter.ts

@@ -0,0 +1,23 @@
+import { defineService, implement, procedure } from "@wrnexus/rpc";
+import { v } from "@wrnexus/validation";
+
+export const greeter = defineService({
+  name: "greeter",
+  procedures: {
+    greet: procedure
+      .input(v.object({ name: v.string() }))
+      .output<{ message: string; subject: string }>()
+      .build(),
+  },
+});
+
+export default implement(
+  greeter,
+  {
+    greet: async ({ name }, ctx) => ({
+      message: `Hello, ${name}`,
+      subject: ctx.subject?.subjectId ?? "anonymous",
+    }),
+  },
+  { selfApp: "auth-showcase" },
+);

examples/auth-showcase/package.json

@@ -13,6 +13,7 @@
   "dependencies": {
     "@wrnexus/auth": "workspace:*",
     "@wrnexus/authz": "workspace:*",
+    "@wrnexus/rpc": "workspace:*",
     "@wrnexus/captcha": "workspace:*",
     "@wrnexus/core": "workspace:*",
     "@wrnexus/validation": "workspace:*"