Upgrade Hugo to 0.169.0 (#26496)

Pin Docker builds and Netlify previews to Hugo 0.169.0. Replace
deprecated `.Params.summary` lookups with `.RawSummary` in the guide
template.

Validation: the full minified debug build passed with
`--panicOnWarning`, path checks, and unused-template checks, with no
deprecation notices. Dockerfile and template formatting checks, Markdown
post-processing tests, rendered summary/redirect checks, and API output
validation passed.

Dockerfile

@@ -5,7 +5,7 @@ ARG ALPINE_VERSION=3.23
 ARG GO_VERSION=1.27
 ARG HTMLTEST_VERSION=0.17.0
 ARG VALE_VERSION=3.17.0
-ARG HUGO_VERSION=0.163.0
+ARG HUGO_VERSION=0.169.0
 ARG NODE_VERSION=24
 ARG PAGEFIND_VERSION=1.5.2
 ARG TARGETARCH

layouts/_partials/content-default.html

@@ -1,8 +1,8 @@
 {{ partial "breadcrumbs.html" . }}
 <h1 data-pagefind-weight="10">{{ .Title | safeHTML }}</h1>
-{{- if and (eq .Type "guides") .Params.summary }}
+{{- if and (eq .Type "guides") .RawSummary }}
   <p class="mt-0 text-lg text-gray-500 dark:text-gray-400">
-    {{ .Params.summary }}
+    {{ .RawSummary }}
   </p>
 {{- end }}
 <div class="hidden lg:block">

netlify.toml

@@ -4,7 +4,7 @@ publish = "public"
 [context.deploy-preview.environment]
 NODE_VERSION = "24"
 NODE_ENV = "production"
-HUGO_VERSION = "0.163.0"
+HUGO_VERSION = "0.169.0"
 HUGO_ENABLEGITINFO = "true"
 HUGO_ENVIRONMENT = "preview"
 SECRETS_SCAN_OMIT_PATHS = "public/contribute/file-conventions/index.html"