backstage release v2.88.0

(agent-platform) Create an agent on a Harness picked in the wizard by @QuentinBisson — In the new-agent wizard, the details step offers a Runtime choice among the namespace’s Harnesses, e.g. Claude Code. The platform default stays preselected, and the review names the choice.
(agent-platform, muster) Track cluster and node pool creation; every write through useTrackedMutation by @marians — For operators: portals with TelemetryDeck report creating a cluster and creating a node pool as two new events. Nothing visible changes.
(catalog) Build status processor and declared build toolchain in the catalog by @weatherhog — The catalog table gets a sortable Build toolchain column and an Architect orb filter, and a component’s readiness card says whether its default branch builds (with catalog.processors.buildStatus.enabled).
(scaffolder-backend-module-gs, gs-node) Gs:oci:tagExists scaffolder action by @marians — For template authors: the new action gs:oci:tagExists checks whether a tag exists in an OCI registry, so a template can branch on whether a chart version is published.

(e2e) Agentlab specs pass or skip on a default lab by @teemow — The agentlab browser specs pass, or skip with a reason, on a default lab.

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