fix(layouts): trim whitespace in render-codeblock placeholder/callout branch

Commit d80eb2f (#7069) refactored `layouts/_default/_markup/render-codeblock.html`
to support the new `callout` fence attribute alongside the existing
`placeholders` attribute. The refactor introduced a new conditional
branch that handles placeholder/callout code blocks, but several of its
interior action tags use bare `{{ ... }}` delimiters instead of the
whitespace-trimming `{{- ... -}}` form used in the `else` branch:

    {{- if or .Attributes.placeholders .Attributes.callout -}}
      {{ $code := highlight .Inner .Type }}
      ...
      {{ $code | safeHTML }}

Each non-trimmed action leaks two leading spaces and a trailing newline
into the render-hook output. For a placeholder code block the final
render-hook output then looks like:

    [2 spaces][newline]
    [4 spaces][newline]
    [4 spaces][newline]
    [2 spaces]<div class="highlight">...</div>[newline]

Goldmark sees this as an indented code block preceded by blank lines,
wraps the leading highlighted HTML in `<pre><code>`, and HTML-escapes
every `<` and `>`. The visible symptom is a wall of escaped
`<span class="line">...` fragments on every page with a placeholder or
callout code block, including every InfluxDB 3 sample-data page, the
enterprise backup-restore page, the clustered users/add page, and
about 18 other admin pages. The regression landed on Apr 8 with #7069
and was reported as #7079.

Fix: apply `{{- ... -}}` whitespace trimming to every action inside the
placeholder/callout branch, matching the pattern the `else` branch
already uses. No content files change. Verified with a local Hugo 0.149
build — every previously affected page now renders with zero escaped
highlight blocks, and the site-wide count of pages containing
`&lt;div class=&quot;highlight` drops from 23 to 0.

Closes #7079

Author: claude

layouts/_default/_markup/render-codeblock.html

@@ -1,16 +1,16 @@
 {{ $result := transform.HighlightCodeBlock . }}
 {{- if or .Attributes.placeholders .Attributes.callout -}}
-  {{ $code := highlight .Inner .Type }}
+  {{- $code := highlight .Inner .Type -}}
   {{- if .Attributes.placeholders -}}
-    {{ $placeholderReplace := print "<div data-component='code-placeholder' class='code-placeholder-wrapper'><var title='Edit $0' class='code-placeholder' data-code-var='$0' data-code-var-value='$0' data-code-var-escaped=\"$0\">$0<span class='code-placeholder-edit-icon cf-icon Pencil'></span></var></div>" }}
-    {{ $code = replaceRE .Attributes.placeholders $placeholderReplace $code }}
+    {{- $placeholderReplace := print "<div data-component='code-placeholder' class='code-placeholder-wrapper'><var title='Edit $0' class='code-placeholder' data-code-var='$0' data-code-var-value='$0' data-code-var-escaped=\"$0\">$0<span class='code-placeholder-edit-icon cf-icon Pencil'></span></var></div>" -}}
+    {{- $code = replaceRE .Attributes.placeholders $placeholderReplace $code -}}
   {{- end -}}
   {{- if .Attributes.callout -}}
-    {{ $color := index .Attributes "callout-color" | default "green" }}
-    {{ $calloutReplace := print "<span class='code-callout " $color "'>$0</span>" }}
-    {{ $code = replaceRE .Attributes.callout $calloutReplace $code }}
+    {{- $color := index .Attributes "callout-color" | default "green" -}}
+    {{- $calloutReplace := print "<span class='code-callout " $color "'>$0</span>" -}}
+    {{- $code = replaceRE .Attributes.callout $calloutReplace $code -}}
   {{- end -}}
-  {{ $code | safeHTML }}
+  {{- $code | safeHTML -}}
 {{- else -}}
   {{- $wrapped := string $result.Wrapped -}}
   {{- if in $wrapped "tc-dynamic-values" -}}