v0.6.0: Startup resilience, kubelet clamp CI, and diagnostics improvements

Changelog (v0.6.0)

Summary

v0.6.0 improves pod-node startup robustness, adds CI smoke coverage for kubelet flag clamping, and expands operational diagnostics/documentation for vCluster Platform Auto Nodes.

Added

• Added PODNODE_PODS support in kubelet clamp logic to set --max-pods.
• Added startup fail-fast checks in podnode-entrypoint.sh to verify required executables exist before continuing.
• Added CI workflow (.github/workflows/ci.yaml) with:
  • shell syntax checks
  • clamp smoke test execution
• Added smoke test script (tests/smoke-clamp.sh) to validate kubeadm flag patching behavior.

Changed

• Refactored Docker image setup to use file-based scripts rather than large inline Dockerfile heredocs.
• Updated clamp script to patch kubelet args idempotently (replace existing managed flags before re-adding).
• Added testability overrides to clamp script:
  • PODNODE_KUBEADM_FLAGS_PATH
  • PODNODE_HOST_CPU_CORES
  • PODNODE_HOST_MEM_KI
• Reverted to stable cgroup startup flow (unshare + helper scripts) after runtime instability with the no-escape variant.
• Made cgroup setup more tolerant:
  • create-kubelet-cgroup.sh now warns and drains remaining root cgroup PIDs into init.scope instead of exiting hard.

Removed

• Removed deprecated GitHub Actions ::set-output usage from release workflow.

Documentation

• Updated README with:
  • env-based sizing guidance (PODNODE_CPU, PODNODE_MEMORY, PODNODE_PODS)
  • vCluster Platform Auto Nodes / Pod NodeProvider configuration pattern
  • clarified allocatable vs capacity behavior in this model
  • runtime diagnostics commands for troubleshooting startup/clamp behavior

Notes

• In this pod-node model, CPU/memory allocatable is clamped from env values; CPU/memory capacity may still reflect host-detected values.
• For best consistency, keep NodeProvider resources.requests == resources.limits (Guaranteed QoS).