Refactor meta description handling in head.html for clarity and consistency

Author: madeline-underwood

themes/arm-design-system-hugo-theme/layouts/partials/head/head.html

@@ -26,13 +26,10 @@
 <link rel="canonical" href="https://learn.arm.com{{ .Permalink }}" />
 <title>{{ $title }}</title>
 
-{{/* Meta description: short, task-oriented summary for SERP and AI selection.
-     This is intentionally distinct from the JSON-LD description. */}}
-{{- with .Params.description -}}
-  {{- $d := . | plainify | htmlEscape | trim " \t\r\n" -}}
-  {{- if gt (len $d) 0 -}}
-    <meta name="description" content="{{ $d }}">
-  {{- end -}}
+{{/* Meta description */}}
+{{- $d := .Params.description | default "" | plainify | htmlEscape | strings.TrimSpace -}}
+{{- if gt (len $d) 0 -}}
+<meta name="description" content="{{ $d }}">
 {{- end -}}
 
 {{ partial "head/jsonld.html" . }}