feat(example): add tool list changed notification example

[Nishant-Chaudhary5338]

Summary

Adds a self-contained, runnable example that demonstrates the complete notifications/tools/list_changed flow end-to-end.

Closes #1132

---

What this adds

examples/client/src/toolListChanged.ts (~115 lines)

A single file that:

1. Creates an McpServer pre-loaded with one tool (get_weather)
2. Creates a Client with listChanged.tools.onChanged registered
3. Connects both via InMemoryTransport.createLinkedPair() — no networking, no spawned process
4. After 500 ms, calls server.registerTool('get_forecast', ...) — McpServer internally calls sendToolListChanged() on all connected sessions
5. Client receives notifications/tools/list_changed, re-fetches the tool list, and logs both tools

Expected output:

[server] started with 1 tool: get_weather
[client] connected. initial tools: [ 'get_weather' ]
[server] registering new tool: get_forecast
[client] tool list changed — updated tools: [ 'get_weather', 'get_forecast' ]

Run it:

pnpm --filter @modelcontextprotocol/examples-client exec tsx src/toolListChanged.ts

Why InMemoryTransport

Previous attempts at addressing #1132 added documentation. A runnable file is stronger evidence — reviewers and users can execute it and see the notification lifecycle in real time. InMemoryTransport keeps the example zero-dependency (no server process, no port binding, works anywhere the SDK's test suite runs).

Key implementation notes

• debounceMs: 0 — the default 300 ms debounce is correct for production (coalesces rapid registrations) but makes example output non-deterministic. Setting it to 0 is documented with a comment.
• changedOnce promise — gates teardown on the callback firing rather than a fixed sleep, so the example is deterministic regardless of host speed.
• tsconfig.json paths — added source-level path mappings for @modelcontextprotocol/server (matching the existing pattern for @modelcontextprotocol/client) so tsgo resolves to source during the pre-push typecheck, which runs in parallel with the build job.

Checks

• pnpm --filter @modelcontextprotocol/examples-client run check (typecheck + lint + prettier) ✅
• pnpm -r typecheck (all 13 packages) ✅
• Example runs and produces the expected 4-line output ✅

Note on pre-push hook: The Build job in the hook fails with SIGABRT in packages/middleware/node — reproduced on main with no changes, so it is a pre-existing environment issue unrelated to this PR. Typecheck and Lint both pass.

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