backstage release v3.13.0

Added

• (agent-platform) Change Harness on the agent page, and earlier-revision sessions marked by @QuentinBisson — Change Harness… in an agent’s actions menu moves it to another runtime after showing whether it can run there. On the agent’s Sessions tab, sessions started before the change are marked Earlier revision. Needs agent-manager 2.7.0 or later.
• (agent-platform, gs-backend) Plugins on the agent wizard’s skills step by @teemow — Where the skill repositories hold plugins, the new agent wizard’s step becomes Select skills and plugins: a Claude Code plugin is picked whole, an Agent Plugins package skill by skill. Edit keeps an agent’s plugins. Needs agent-manager 2.6 or later.

Development and CI/CD

• (deps) Refresh vulnerable transitive dependencies by @QuentinBisson
• (e2e) Scope the connector address error to its field by @teemow — The agentlab form-validation spec checks the connector address error on its own field, so it no longer fails because the screen-reader announcement repeats the same text.

Full Changelog: https://github.com/giantswarm/backstage/compare/v3.12.0...v3.13.0