Add an example or template

Each library item is one folder in examples/library/<slug>/. The card, the detail page, the thumbnail and the “Open in editor” link all come from that folder.

1. Build the project with the CLI as docs/agent-authoring.md describes: npm run build:cli, then create and small apply batches into examples/library/<slug>/project.json. Save each batch in ops/, and use the title as the project name.
2. Apply the suggestedOps the diagnostics give, until validate --fail-on warning exits 0.
3. Render with render --out, look at the drawings, and copy the best one to drawings/overview.png.
4. Write meta.json with slug, kind (template or example), title, description, level, tags, learn, order and thumbnail.
5. Run npm run docs:check and npm test, then npm run docs:build.

Caution

The docs build validates every item with the current engine. If an engine change makes one invalid, the build fails and names the item and the diagnostic. Fix the item, not the check.

The app bundles the project, so /open?template=<slug> works as soon as the app is rebuilt.