use variable fixed width for quote wrapper top rule to avoid visual regressions

Author: jmuzina

templates/_macros/shared/vf_section_top_rule.jinja

@@ -1,14 +1,19 @@
 # Helper macro to render a top rule for a section.
 # Parameters:
-#  - top_rule_variant: string, one of "default", "muted", "highlighted", "none"
-{%- macro vf_section_top_rule(top_rule_variant="default") -%}
+#   - top_rule_variant("default" | "muted" | "highlighted" |"none"): variant of horizontal rule to use
+#   - is_fixed_width(Boolean): Whether to constrain the rule by the fixed content width. Default to False.
+#       If you don't use this, you should wrap the rule in a .grid-row.
+{%- macro vf_section_top_rule(
+  top_rule_variant="default",
+  is_fixed_width=False
+) -%}
   {%- set top_rule_variant = top_rule_variant | trim | lower -%}
   {%- if top_rule_variant not in ["default", "muted", "highlighted", "none"] -%}
     {%- set top_rule_variant = "default" -%}
   {%- endif -%}
 
   {%- if top_rule_variant != "none" -%}
-    {%- set top_rule_classes = "p-rule is-fixed-width" -%}
+    {%- set top_rule_classes = "p-rule" -%}
     {%- if top_rule_variant != "default" -%}
       {#-
         p-rule--highlighted doesn't exist (use p-rule--highlight instead), but p-rule--muted does.
@@ -23,6 +28,10 @@
     {%- endif -%}
   {%- endif -%}
 
+  {%- if is_fixed_width -%}
+    {%- set top_rule_classes = top_rule_classes + " " + "is-fixed-width" -%}
+  {%- endif -%}
+
   {%- if top_rule_variant != "none" -%}
     <hr class="{{- top_rule_classes -}}"/>
   {%- endif -%}

templates/_macros/vf_quote-wrapper.jinja

@@ -266,7 +266,7 @@
   <div class="p-section{% if is_shallow %}--shallow{% endif %}">
     {#- pattern-level separator -#}
     {%- if has_heading_row -%}
-      {{ vf_section_top_rule("default") }}
+      {{ vf_section_top_rule(top_rule_variant="default", is_fixed_width=True) }}
     {%- endif -%}
     {{- _quote_wrapper_heading_block(
         heading={