fix: support multiple paths in KUBECONFIG

[kri5]

KUBECONFIG may list several kubeconfig files to merge, but the whole value was used as a single path: clientcmd got it as ExplicitPath, and auto-detect ran os.Stat on the joined string, so Gonzo silently fell back to system logs.

Let client-go resolve the location instead of reimplementing it. BuildClientset now starts from NewDefaultClientConfigLoadingRules, which splits and merges KUBECONFIG and falls back to ~/.kube/config, and sets ExplicitPath only for --k8s-kubeconfig. As in kubectl, that flag stays a single file; merging is a KUBECONFIG feature. Auto-detect loads the merged config and checks that it holds at least one context.

Closes #147

[Copilot]

🟢 Approval recommended

The core behavior change is correct and covered by a focused unit test, with only minor follow-up nits noted in review comments.

Pull request overview

Updates Gonzo’s Kubernetes kubeconfig handling to correctly support KUBECONFIG values containing multiple paths by delegating splitting/merging behavior to client-go’s standard loading rules, aligning behavior with kubectl.

Changes:

• Switch kubeconfig resolution in BuildClientset to clientcmd.NewDefaultClientConfigLoadingRules() and only set ExplicitPath for --k8s-kubeconfig.
• Update auto-detection to load the merged kubeconfig and require at least one context before enabling Kubernetes streaming.
• Add unit tests for multi-path KUBECONFIG behavior and update docs/help text to describe the new default behavior.

File summaries

File	Description
README.md	Updates CLI flag documentation to reflect $KUBECONFIG-aware default kubeconfig behavior.
internal/k8s/config.go	Uses client-go loading rules for kubeconfig detection and clientset construction (supports merged configs).
internal/k8s/config_test.go	Adds coverage for DetectKubeconfig across single/multi-path and missing/empty config cases.
guides/KUBERNETES_USAGE.md	Documents multi-path KUBECONFIG merging behavior and updates kubeconfig default text.
cmd/gonzo/app.go	Updates log-source auto-detection to use merged kubeconfig detection instead of os.Stat on a single path string.

Review details

• Files reviewed: 5/5 changed files
• Comments generated: 2
• Review effort level: Lite

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[lucasMesquitaBorges]

LGTM!