agent-platform release v4.6.0

The kagent controller GRPCRoute matches by gRPC service again — one service-only match per service of kagent.controllerRoute.grpc.services (the five services with empty method lists by default), which the agentgateway controller of chart 2.1.1 (the Giant Swarm line’s v1.5.1-gs.3, carrying the GRPCRoute translation fix) turns into the path prefix /<service>/; a service with RPCs listed keeps one exact service/method match per RPC, the fallback for an installation whose agentgateway chart is older and a way to expose a subset. The 39-RPC enumeration #345 shipped as a workaround is gone from the default; an RPC the kagent line adds is reachable without a values change. Needs the agentgateway component at chart ≥ 2.1.1 (the meta chart’s components.agentgateway.versionRange 2.x resolves it; the render cannot check the controller’s version). make verify-kagent-route asserts the default and the fallback.