fix(ci): add path offset to product-name and sidebar for PR previews

Apply the same prPreviewPathOffset fix to product-name.html and
sidebar.html that was applied in the initial PR #6665.

These templates parse RelPermalink to detect product context, but when
baseURL includes a subdirectory path (e.g., /docs-v2/pr-preview/pr-XXXX/),
the path indices shift. This fix uses the configurable offset to skip
extra path segments in PR preview builds.

Author: jstirnaman

layouts/partials/sidebar.html

@@ -1,8 +1,10 @@
 {{ $currentPage := . }}
 {{ $productPathData := findRE "[^/]+.*?" .RelPermalink }}
-{{ $product := index $productPathData 0 }}
+{{/* Support deployments (such as CI tools) with subdirectory baseURL */}}
+{{ $pathOffset := .Site.Params.prPreviewPathOffset | default 0 }}
+{{ $product := index $productPathData (add $pathOffset 0) }}
 {{ $productName := (index .Site.Data.products $product).name }}
-{{ $currentVersion := index $productPathData 1 }}
+{{ $currentVersion := index $productPathData (add $pathOffset 1) }}
 
 <!-- Menu Key -->
 {{ .Scratch.Set "menuKey" "menu"}}

layouts/shortcodes/product-name.html

@@ -1,5 +1,7 @@
 {{- $productPathData := findRE "[^/]+.*?" .Page.RelPermalink -}}
-{{- $currentProduct := index $productPathData 1 -}}
+{{- /* Support deployments (such as CI tools) with subdirectory baseURL */ -}}
+{{- $pathOffset := .Site.Params.prPreviewPathOffset | default 0 -}}
+{{- $currentProduct := index $productPathData (add $pathOffset 1) -}}
 {{- $length := .Get 0 | default "long" -}}
 {{- $omit := .Get "omit" | default "" -}}
 {{- $scratch := newScratch -}}