fix(schema): stop fabricating VideoObject uploadDate from git info and now (#20904)

video-entity.html was the one schema collector still holding the pattern
the rest of this PR removes: uploadDate fell back to .GitInfo.AuthorDate
and then to now() whenever a page had no front-matter date, fabricating an
upload date from a "last touched" timestamp (or, on a shallow CI checkout,
stamping every dateless page as uploaded today).

uploadDate is required for VideoObject, so unlike datePublished it can't
simply be omitted. Instead the entity is skipped entirely when there's no
explicit front-matter date, and the date now comes only from .PublishDate
(which resolves front-matter date/publishDate) rather than .Date, whose
resolution chain can reach the lastmod key. graph-builder.html already
guards against an empty collector result, so a skipped entity is a no-op
in the @graph.

Co-authored-by: claude[bot] <claude[bot]@users.noreply.github.com>
Co-authored-by: Claude Opus 5 <noreply@anthropic.com>

Author: 3 people

layouts/partials/schema/collectors/video-entity.html

@@ -29,21 +29,27 @@
 
 {{/* Generate VideoObject schema for first video only (primary video) */}}
 {{ $schema := dict }}
-{{ if gt (len $videos) 0 }}
+
+{{/* Get the upload date, but only from a real source of truth: an explicit
+     front-matter date/publishDate (Hugo's .PublishDate resolves both). Never
+     from git info, since a page's git history reflects when it was last
+     *touched*, not when its video was uploaded, and never from `now`, which
+     on an absent git history (e.g. a shallow CI checkout) would stamp every
+     page as uploaded today. Unlike datePublished in the article/blog/FAQ
+     collectors, uploadDate is required for VideoObject, so it can't simply be
+     omitted — when there's no real date we skip emitting the entity entirely
+     rather than publish an invalid or fabricated one. Mirrors the date policy
+     in schema/collectors/article-entity.html. */}}
+{{ $publishDate := "" }}
+{{ if and .PublishDate (ne (.PublishDate.Format "2006-01-02") "0001-01-01") }}
+  {{ $publishDate = .PublishDate }}
+{{ end }}
+
+{{ if and (gt (len $videos) 0) $publishDate }}
   {{ $primaryVideoId := index $videos 0 }}
   {{ $videoTitle := .Title }}
   {{ $videoDescription := or .Params.meta_desc .Summary (printf "Video content for: %s" .Title) }}
 
-  {{/* Get publish date with fallback */}}
-  {{ $publishDate := .Date }}
-  {{ if or (not $publishDate) (eq ($publishDate.Format "2006-01-02") "0001-01-01") }}
-    {{ if and .GitInfo .GitInfo.AuthorDate }}
-      {{ $publishDate = .GitInfo.AuthorDate }}
-    {{ else }}
-      {{ $publishDate = now }}
-    {{ end }}
-  {{ end }}
-
   {{/* Build video schema */}}
   {{ $schema = dict
     "@type" "VideoObject"