refactor(admonition): simplify title handling logic

Replace complex title processing (9 lines) with single-line title filter approach.

Changes:
- Simplify $admonitionTitle definition from 5 variables to 1 line
- Remove $titleClass conditional logic (4 lines)
- Replace dynamic CSS class with static "grow" class
- Use Hugo title filter instead of CSS capitalize
- Remove TrimSpace processing per author feedback

This maintains the same visual behavior while significantly reducing code complexity.

Related: PR #2704 feedback from ZhenShuo2021

layouts/_default/_markup/render-blockquote.html

@@ -33,19 +33,11 @@
   {{- $normalizedType := index $typeMap $rawType | default $rawType -}}
   {{- $iconName := .Attributes.icon | default (index $iconMap $normalizedType) | default "circle-info" -}}
 
-  {{- $rawCustomTitle := .AlertTitle | default "" -}}
-  {{- $trimmedCustomTitle := strings.TrimSpace $rawCustomTitle -}}
-  {{- $hasCustomTitle := ne $trimmedCustomTitle "" -}}
-  {{- $defaultTitle := i18n (printf "admonition.%s" $normalizedType) | default $normalizedType -}}
-  {{- $admonitionTitle := cond $hasCustomTitle $rawCustomTitle $defaultTitle -}}
+  {{- $admonitionTitle := .AlertTitle | default ((i18n (printf "admonition.%s" $normalizedType) | default $normalizedType) | title) -}}
 
   {{- $containerClass := "admonition relative overflow-hidden rounded-lg border-l-4 my-3 px-4 py-3 shadow-sm" -}}
   {{- $headerClass := "flex items-center gap-2 font-semibold text-inherit" -}}
   {{- $contentClass := "admonition-content mt-3 text-base leading-relaxed text-inherit" -}}
-  {{- $titleClass := "grow" -}}
-  {{- if not $hasCustomTitle -}}
-    {{- $titleClass = printf "%s %s" $titleClass "capitalize" -}}
-  {{- end -}}
 
   {{- $isCollapsible := in (slice "+" "-") .AlertSign -}}
   {{- if $isCollapsible -}}
@@ -57,7 +49,7 @@
         <div class="flex shrink-0 h-5 w-5 items-center justify-center text-lg">
           {{- partial "icon.html" $iconName -}}
         </div>
-        <div class="{{ $titleClass }}">
+        <div class="grow">
           {{ $admonitionTitle }}
         </div>
         <div
@@ -77,7 +69,7 @@
         <div class="flex shrink-0 h-5 w-5 items-center justify-center text-lg">
           {{- partial "icon.html" $iconName -}}
         </div>
-        <div class="{{ $titleClass }}">
+        <div class="grow">
           {{ $admonitionTitle }}
         </div>
       </div>