[codex] Support PDB and rollout strategy in chart

[vigneshrajsb]

Summary

• Add optional strategy rendering for g2krelay and each named g2krepeater Deployment.
• Add optional PodDisruptionBudget templates for g2krelay and each named g2krepeater instance.
• Remove legacy single g2krepeater values compatibility; use the g2krepeaters map only.
• Document the new values and add helm-unittest coverage for Deployment strategy and PDB rendering.
• Bump chart version to 0.8.0 and update README install examples.

Publishing

The chart is published by .github/workflows/helm-release.yml. After this PR merges to main, changes under helm/chart/** trigger the workflow, which packages helm/chart and runs:

helm push g2k-0.8.0.tgz oci://ghcr.io/vmelikyan

That publishes the chart at oci://ghcr.io/vmelikyan/g2k --version 0.8.0. Docker images are separate and only publish from the release workflow when a GitHub Release is published.

Validation

• helm lint helm/chart --set g2krelay.envVars.WEBHOOK_SECRET=test
• helm unittest helm/chart
• env GOCACHE=/tmp/gocache-g2k-repeater go test ./... from g2krepeater/
• env GOCACHE=/tmp/gocache-g2k-relay go test ./... from g2krelay/