Add lazy-auth-server example (#679)

Adds an example MCP App server demonstrating lazy (on-demand) OAuth:
the server connects and lists tools without authentication, and only
prompts for auth when a protected tool is called, by responding 401
with a WWW-Authenticate header pointing at protected-resource metadata.

- Public `show_auth_button` app calls the protected `get_secret` tool
  via callServerTool; the host runs the OAuth flow on 401 and retries
- Embedded mock authorization server (authorization-code + PKCE,
  short-lived HS256 tokens, refresh + session revocation) so the whole
  flow runs from a single process
- TTL-scoped endpoint paths (/ttl/<seconds>/mcp) let slow or automated
  clients request longer-lived tokens per connection, threaded through
  OAuth via RFC 8707 resource indicators
- `elicit_url` / `elicit_by_error` tools demonstrating URL elicitation

examples/lazy-auth-server/tsconfig.server.json

@@ -0,0 +1,17 @@
+{
+  "compilerOptions": {
+    "target": "ES2022",
+    "lib": ["ES2022"],
+    "module": "NodeNext",
+    "moduleResolution": "NodeNext",
+    "declaration": true,
+    "emitDeclarationOnly": true,
+    "outDir": "./dist",
+    "rootDir": ".",
+    "strict": true,
+    "skipLibCheck": true,
+    "esModuleInterop": true,
+    "resolveJsonModule": true
+  },
+  "include": ["server.ts"]
+}