docs: fix basic-host setup instructions in quickstart

[rafa-thayto]

Summary

• Add missing npm install and npm run build steps at the ext-apps root before running the basic-host example
• Without these steps, basic-host fails because it imports from ../../../dist/src/ which doesn't exist

Problem

Following the current quickstart instructions:

git clone https://github.com/modelcontextprotocol/ext-apps.git
cd ext-apps/examples/basic-host
npm install
npm start

Results in build failures because:

1. The basic-host imports from ../../../dist/src/
2. The dist directory doesn't exist until the root package is built
3. Building requires dev dependencies (like ts-to-zod) that aren't installed when only running npm install in the example directory

Solution

Updated instructions to include root-level setup:

git clone https://github.com/modelcontextprotocol/ext-apps.git
cd ext-apps
npm install
npm run build
cd examples/basic-host
npm start

Test Plan

• Follow the updated quickstart instructions from scratch
• Verify basic-host starts successfully at http://localhost:8080
• Verify the get-time tool works correctly

[jonathanhefner]

One nit. 🙏

[rafa-thayto]

One nit. 🙏

done! @jonathanhefner

[jonathanhefner]

Thank you, @rafa-thayto!