Docs: turnkey Kubernetes debugging recipe (example manifests + attach presets)

[debugmcpdev]

Motivation

The capability has shipped: the Docker image debugs seven languages, attach modes work without local toolchains, and ephemeral-container sidecar debugging on Kubernetes is verified (kubectl debug --profile=general injecting SYS_PTRACE, attaching to PID 1, resolving symbols through /proc/1/root, rdbg attach over kubectl port-forward). What's missing is the copy-paste path from "my pod is misbehaving" to "agent is stepping through it".

Deliverables

1. docs/kubernetes.md — a walkthrough against a sample Deployment:
   • ephemeral sidecar attach: the kubectl debug flags that matter (--profile=general, -- entrypoint replacement), why SYS_PTRACE and a shared PID namespace are needed
   • remote attach via port mapping / kubectl port-forward (the rdbg pattern, generalized to other attach-capable adapters)
   • symbol resolution notes (/proc/<pid>/root), ptrace_scope, distroless-image caveats
2. Example manifests (or a minimal Helm chart) under examples/kubernetes/: target app + sidecar spec + the MCP client configuration to reach the debugger.
3. Preset attach configs per attach-capable language, so agents don't have to derive them each time.

Existing material to build on: docs/docker-support.md, docs/ruby/README.md (remote attach), and the container e2e suite.