agent-platform release v4.8.1

A deleted platform Harness is recreated by the kagent release on its next reconcile (giantswarm/agent-platform#409): the kagent HelmRelease carries spec.driftDetection.mode: enabled — on every reconcile (gitops.interval) helm-controller compares the release manifest with the cluster and re-applies what differs or is missing, as a server-side apply without a Helm revision. Without it a plain reconcile of the unchanged release reported “in-sync”, and the Harness a consumer skipping 4.7.19 lost on the 4.8.0 upgrade stayed deleted — every template unadmitted, 600 s observed — until a forced reconcile. components.<name>.driftDetection is a passthrough for every component entry (HelmRelease v2 spec.driftDetection: mode, ignore), set for kagent only; tests/verify-kagent-wiring.py asserts it and that no other release carries one by default, and the ATS smoke deletes the Harness and sees it back on a requested (not forced) reconcile with both templates Ready and no revision written. UPGRADE.md’s 4.8.0 note names the forced-reconcile recovery for an installation on 4.8.0 exactly; the customer BOM example pins the connectivity chart to the release it is published with.