Index table re-derives the generator's publish rule, so the two can silently disagree

[TineoC]

Problem

Two templates independently decide which KEPs are publishable, using two copies of the same rule (stage in alpha/beta/stable/deprecated or status in implementable/implemented).

• content/en/resources/keps/_content.gotmpl uses it to decide whether to AddPage.
• layouts/shortcodes/keps-data.html uses its own copy ($hasPage) to decide whether a row links to /resources/keps/N/ or falls back to features.k8s.io/N.

$hasPage never checks that the page exists — it predicts what the generator did by re-deriving the same rule.

Suggested fix

One partial owning the rule, both callers reading it:

{{/* layouts/partials/kep-data.html — returns the filtered KEP slice */}}
{{- $out := slice -}}
{{- range $kep := $kepData -}}
  {{- if or (in $validStages $kep.stage) (in $validStatuses $kep.status) -}}
    {{- $out = $out | append $kep -}}
  {{- end -}}
{{- end -}}
{{- return $out -}}