backstage release v2.88.0-rc.4

Added

• (scaffolder-backend-module-gs,gs-node) Gs:oci:tagExists scaffolder action in #2717 by @marians
• (agent-platform,muster) Track cluster and node pool creation; every write through useTrackedMutation in #2718 by @marians
• (agent-platform) Create an agent on a Harness picked in the wizard in #2637 by @QuentinBisson
• (catalog) Build status processor and declared build toolchain in the catalog in #2271 by @weatherhog

Changed

• (e2e) Agentlab specs pass or skip on a default lab in #2716 by @teemow

Full Changelog: https://github.com/giantswarm/backstage/compare/v2.87.0...v2.88.0-rc.4