[css-borders-4] Adjust border-width zero value special case per WG resolution. #11494 (#13208)

Co-authored-by: Kevin Babbitt <kbabbitt@KBABBITT-MBP25.local>

Author: kbabbitt

css-borders-4/Overview.bs

@@ -371,7 +371,7 @@ Line Thickness: the 'border-width' properties</h3>
 	Inherited: no
 	Logical property group: border-width
 	Percentages: N/A
-	Computed value: absolute length, [=snapped as a border width=]; zero if the border style is ''border-style/none'' or ''border-style/hidden''
+	Computed value: absolute length, [=snapped as a border width=]
 	Animation Type: by computed value
 	</pre>
 
@@ -386,6 +386,11 @@ Line Thickness: the 'border-width' properties</h3>
 	The <dfn>thin</dfn>, <dfn>medium</dfn>, and <dfn>thick</dfn> keywords
 	are equivalent to ''1px'', ''3px'', and ''5px'', respectively.
 
+	The [=resolved value=] for the 'border-width' properties is the [=used value=].
+
+	If the 'border-style' corresponding to a given 'border-width' is ''border-style/none'' or ''border-style/hidden'',
+	then the [=used value|used=] width is 0.
+
 	The [=flow-relative=] properties
 	'border-block-start-width',
 	'border-block-end-width',
@@ -3245,6 +3250,9 @@ First Public Working Draft</a> of 22 July 2025
 	* Renamed <css>normal</css> value of 'border-*-clip' properties to ''border-top-clip/none''
 	* Added new syntax for 'border-*-*-radius' longhands using a slash to separate horizontal and vertical radii
 	* Allowed a single <<length>> value for 'box-shadow-offset' to set both offsets to the same value
+	* Changed the special case of 'border-width' having a value of ''0'' when 'border-style' is ''border-style/none'' or ''border-style/hidden''
+		from a computed-value effect to a resolved-value effect.
+		(<a href="https://github.com/w3c/csswg-drafts/issues/11494">Issue 11494</a>)
 
 <h3 class=no-num id="level-changes">
 Additions since [[CSS3BG]]</h3>