Docs: replace spread/euler demo cards with ELK

[Copilot]

The docs demo gallery still highlighted spread and euler, while the desired layout showcase should promote elk instead. This updates the gallery entries to remove the older layout cards and add ELK with a dedicated thumbnail and direct link to the extension demo.

• Demo gallery updates

  • removed the Spread layout and Euler layout cards from the docs gallery source
  • added an ELK layout card
  • pointed the ELK card at the existing layered demo in cytoscape.js-elk

• Docs assets

  • added a new documentation/img/demos/elk-layout.png thumbnail for the ELK card

• Source change

  { "name": "ELK layout", "id": "elk-layout", "github": "cytoscape/cytoscape.js-elk", "viewUrl": "https://cytoscape.github.io/cytoscape.js-elk/?demo=layered" }

• Screenshot
  

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• cdn.jsdelivr.net
  • Triggering command: /usr/bin/curl curl -L REDACTED -o elk.bundled.js (dns block)
• cytoscape.github.io
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node /home/REDACTED/work/_temp/ghcca-node/node/bin/node --enable-source-maps /home/REDACTED/work/_temp/copilot-developer-action-main/dist/index.js (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)