build: bump Hugo to 0.162.1 and fix deferred CSS template (#25264)

## Summary

The site fails to build on Hugo 0.162, which no longer allows
`templates.Defer` inside a `partialCached` partial. `head.html` called
`utils/css.html` (which defers with a global key) via `partialCached`.
This switches that call to `partial` — the global Defer key already
dedupes the work, so caching was redundant — and bumps the pinned Hugo
version in the `Dockerfile` and `netlify.toml` to 0.162.1.

Verified with a full local build on Hugo 0.162.1 extended (Node 24):
clean build, 3332 pages, no template errors.

## Learnings

- Hugo 0.162 enforces that `templates.Defer` cannot live inside a
`partialCached` partial; the build error points at the deferred
template, not the `partialCached` caller, so trace upward to the caching
call site.

Generated by Claude Code

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Dockerfile

@@ -5,7 +5,7 @@ ARG ALPINE_VERSION=3.23
 ARG GO_VERSION=1.26
 ARG HTMLTEST_VERSION=0.17.0
 ARG VALE_VERSION=3.11.2
-ARG HUGO_VERSION=0.161.1
+ARG HUGO_VERSION=0.162.1
 ARG NODE_VERSION=24
 ARG PAGEFIND_VERSION=1.5.2
 

layouts/_partials/head.html

@@ -16,7 +16,7 @@
     />
   {{- end -}}
 {{ end -}}
-{{ partialCached "utils/css.html" "-" "-" }}
+{{ partial "utils/css.html" . }}
 <link href="/pagefind/pagefind-component-ui.css" rel="stylesheet" />
 {{- if hugo.IsProduction -}}
   <script

netlify.toml

@@ -4,7 +4,7 @@ publish = "public"
 [context.deploy-preview.environment]
 NODE_VERSION = "24"
 NODE_ENV = "production"
-HUGO_VERSION = "0.161.1"
+HUGO_VERSION = "0.162.1"
 HUGO_ENABLEGITINFO = "true"
 HUGO_ENVIRONMENT = "preview"
 SECRETS_SCAN_OMIT_PATHS = "public/contribute/file-conventions/index.html"