docs: clarify listener metric label sources

[ChongZhe001025]

Summary

Clarifies the listenerMetrics examples in the gha-runner-scale-set chart values.

Based on the current implementation, gauge metrics such as gha_running_jobs, gha_assigned_jobs, and gha_registered_runners are recorded from scale set statistics using scale set labels. These labels come from the configured GitHub scope.

Counter and histogram metrics such as gha_started_jobs_total, gha_completed_jobs_total, and job duration metrics are recorded from job messages, so they can include job-level metadata such as repository and workflow information.

Context

Refs #4304.

While investigating the issue, I found that:

• NewExporter() is called from cmd/ghalistener/main.go

• ExporterConfig.Repository, ExporterConfig.Organization, and ExporterConfig.Enterprise are derived from actions.ParseGitHubConfigFromURL(config.ConfigureURL)

• config.ConfigureURL comes from the listener config secret generated from AutoscalingRunnerSet.Spec.GitHubConfigUrl

• ParseGitHubConfigFromURL() populates scope values based on the configured URL:

  • /org/repo populates repository scope
  • /org populates organization scope
  • /enterprises/foo populates enterprise scope

Because of this, gauge metrics appear to reflect the configured scale set scope rather than per-job metadata. This change clarifies that expectation in the chart values examples instead of deriving gauge labels from job messages.

Changes

• Updated charts/gha-runner-scale-set/values.yaml
• Updated charts/gha-runner-scale-set-experimental/values.yaml
• Added comments clarifying that gauge labels come from scale set scope, while counter and histogram labels can come from job messages

Testing

• Ran git diff --check

No Go tests or Helm rendering tests were run because this change only updates commented examples in values.yaml and does not affect rendered manifests or Go behavior.