Publish the devtools example gallery

[SandroMaglione]

Summary

• Build the devtools example machines into the existing GitHub Pages artifact under /devtools/.
• Keep the API reference at the site root and give the gallery its own assets and data directory.
• Document the deployment-order build commands and local preview route.

Changeset

• Added or updated for a library or package-metadata change
• Not required because this PR does not change a publishable package

Validation

• pnpm check
• Automated type-performance measurement was not required
• Automated runtime- and memory-performance measurement was not required
• pnpm docs:site
• Devtools static build generated all 11 example machines
• Main site, /devtools/, and /devtools/machines.json returned HTTP 200 locally