ci: Add GitHub Action to verify Notebook MCP bundle

[snehshah22]

This Pull Request adds a GitHub Action workflow dedicated to the notebook_mcp server to ensure that contributors do not forget to build and commit the compiled distribution bundle.

Since we are pursuing a zero-install strategy via npx pointing directly at the repository source, it is absolutely critical that the generated asset notebook_mcp/dist/index.js honors the latest code edits.

What this workflow does:

1. Triggers exclusively on Pull Requests affecting anything inside the notebook_mcp/ directory.
2. Clones the branch and runs an active npm run bundle from source.
3. Compares the freshly generated script against the copy committed by the PR author via git diff --exit-code.
4. Stays passing if clean, but hard fails the build checks blocking merge if the developer forgot to run build locally!