Add convenient shortcut parameters for Kubernetes pod spec configuration

[Copilot]

Setting full pod_spec_kwargs for common Kubernetes configurations (affinity, tolerations) is verbose and error-prone. This adds shortcut parameters that expand to the full spec.

Changes

• New KubernetesTerminal parameters:

  • affinity_mode: Preset for node affinity ("same_host" schedules on host from env var)
  • affinity_hostname_key: Env var name for hostname lookup (default: "HOSTNAME")
  • tolerations_preset: Single string or list ("spot", "azure_spot", "critical")

• Helper functions:

  • _build_pod_spec_from_shortcuts(): Generates pod spec from shortcuts
  • _deep_merge_dicts(): Merges shortcut spec with explicit pod_spec_kwargs (explicit wins)

• Preset registries: AFFINITY_PRESETS, TOLERATION_PRESETS for extensibility

Example

Before:

terminal = KubernetesTerminal(
    pod_spec_kwargs={
        "affinity": {
            "nodeAffinity": {
                "requiredDuringSchedulingIgnoredDuringExecution": {
                    "nodeSelectorTerms": [{"matchExpressions": [{"key": "kubernetes.io/hostname", "operator": "In", "values": ["{{HOSTNAME}}"]}]}]
                }
            }
        },
        "tolerations": [{"key": "kubernetes.azure.com/scalesetpriority", "operator": "Equal", "value": "spot", "effect": "NoSchedule"}],
    }
)

After:

terminal = KubernetesTerminal(
    affinity_mode="same_host",
    tolerations_preset="spot",
)

Shortcuts and explicit pod_spec_kwargs can be combined; explicit values override shortcuts.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Provide more convenient settings for Kubernetes</issue_title>
<issue_description>At the moment, have to set the full pod_spec_kwargs is a bit annoying. We can support commonly used settings (eg., affinity_mode: "in_host"), etc. </issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Provide more convenient settings for Kubernetes #283

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