prepull.spreadSeconds: 0 is ignored due to sprig default treating 0 as empty

Summary

prepull.spreadSeconds cannot be set to 0. The template uses:

openstudio-server/templates/hooks/image-prepull-daemonset.yaml:7

{{- $spreadSeconds := default 300 (get $prepull "spreadSeconds") -}}

Sprig's default treats 0 as "empty", so spreadSeconds: 0 falls back to 300. The values.yaml comment ("Keep warmup immediate so newly added nodes become usable as soon as possible", prepull.spreadSeconds: 0) does not match the effective behavior (300s pacing).

Impact

• Operators cannot configure immediate warmup; warm-up is always spread (300s default) even when 0 is set.
• Also caused a duplicate-key wart in values.yaml (a stale spreadSeconds: 900 beside the new spreadSeconds: 0), which was cleaned up in 6fd91c7.

Suggested fix

Gate on key presence instead of sprig default, e.g.:

{{- $spreadSeconds := 300 -}}
{{- if hasKey $prepull "spreadSeconds" }}{{ $spreadSeconds = get $prepull "spreadSeconds" }}{{ end -}}

Same pattern appears wherever a numeric value (including 0) must be usable: priorityClasses (see companion issue) and worker_hpa stabilization windows.

Acceptance

• helm template --set prepull.spreadSeconds=0 renders 0 (not 300).

Start with openstudio-server/templates/hooks/image-prepull-daemonset.yaml and inspect how prepull.spreadSeconds is rendered. Run helm template --set prepull.spreadSeconds=0 and verify the rendered DaemonSet uses 0 rather than 300; also check the nearby values.yaml entry for consistency.