agent-platform release v3.14.0

The Argo CD render engine of the meta-package. gitops.engine accepts flux only (enum: [flux] in the schema, a template guard behind it); templates/components.yaml renders a Flux OCIRepository + HelmRelease per component and nothing else; gitops.argo.project / gitops.argo.server are gone from the values and the schema. The Argo Application branch was never verified against a running Argo CD and no installation selected it, and the platform cannot run on Argo CD in any case: agents are Flux objects on every path (the Backstage agent create flow and agent-manager write an OCIRepository + HelmRelease per agent). gitops.engine: argo now fails the render — the schema first, the guard with gitops.engine=argo is not supported; flux is the only engine — and gitops.argo.* fails the schema. make verify-meta asserts the refusal on both layers, that the Flux render carries no argoproj.io object and that an explicit gitops.engine: flux renders exactly the default; the Argo render assertions of verify-meta and verify-presets are gone with the branch. No installation needs to act: the Flux render is byte-identical. See UPGRADE.md.