agent-platform release v4.5.2

components.backstage.versionRange is >=1.0.0 <3.0.0 (was 1.x). The complete kagent API v2 Dev Portal is backstage 2.0.0 — giantswarm/backstage#2344 (the backend’s Connect client against the controller’s gRPC origin, the portal’s sessions and chat) was released as a major, on top of 1.0.0 (the reader, #2343), 1.1.0 (create, #2296) and 1.2.0 (edit/delete, #2298). 1.x resolved 1.2.0, a portal without the gRPC backend that answers the 4.0 controller route with 404s; the range now admits 2.0.0 and stays bounded below the next major. tests/verify-components.py and UPGRADE.md move with it. No installation acts — the component is off by default and the release stays inert behind the fleet’s <4.0.0 bound.