Update "Setup your docs environment" instructions to match current repo layout

[zachcasper]

Summary

The Setup your docs environment section in the docs contribution guide is out of date and points contributors to a Docsy theme directory that no longer exists in this repository layout.

Problem

The guide currently instructs contributors to run:

cd docs
git submodule update --init --recursive
npm install
cd themes/docsy
npm install
cd ..

In the current radius-project/docs repository:

• there is no themes/docsy directory
• npm install fails at the repository root because package.json is not there
• the actual Node project lives under docs/docs
• Docsy is brought in via Hugo Modules rather than a checked-in theme folder
• npm run dev fails because no dev script is defined in docs/package.json

This causes a confusing setup experience for contributors following the documented steps.

Evidence

A local reproduction following the current guide shows:

• npm install fails in docs/ with ENOENT because package.json is missing
• cd themes/docsy fails with no such file or directory
• npm ci succeeds after changing into docs/docs
• npm start successfully launches the local Hugo server from docs/docs
• npm run dev fails because no dev script is defined

Suggested update

Revise the setup steps to match the current repository structure and Hugo Module-based theme usage. At minimum, update the instructions to:

1. clone the repos as needed
2. generate CLI docs
3. change into docs/docs
4. run npm ci
5. run npm start from docs/docs
6. remove the themes/docsy initialization step
7. remove references to npm run dev where no such script exists

Likely files to update

• docs/content/contributing/contributing-docs/index.md
• docs/README.md
• potentially any linked docs pages that duplicate the same outdated setup sequence

Acceptance criteria

• setup instructions no longer reference themes/docsy
• setup instructions use the correct working directory for npm commands
• setup instructions use commands that exist in docs/package.json
• a contributor can follow the documented steps from a fresh clone without hitting missing-directory or missing-package.json errors
• the contribution guide reflects the current Hugo Modules/Docsy setup