v0.2.0 - Production beta foundation

This release turns kctx from an early prototype into a production-beta foundation for structured Kubernetes operational context.

Highlights include a versioned JSON contract, machine-readable schemas, structured error responses, redaction and data-safety hardening, end-to-end golden tests, server observability, request limits, Argo CD and cert-manager adapters, namespace health improvements, graph/context refinements, and long-form documentation.