[css-anchor-position-1] Clarify that intersection area must be non-zero for anchors-visible. w3c#13176

Author: fantasai

css-anchor-position-1/Overview.bs

@@ -2263,6 +2263,9 @@ depending on some commonly needed layout conditions.
 	i.e. clipping due to 'clip-path',
 	'overflow', or other effects (such as [=paint containment=])
 	that clip to the [=overflow clip edge=].
+	If |anchor| has non-zero area,
+	it must also have a non-zero intersection area
+	to be considered not fully clipped.
 
 	Whether or not |anchor| is [=clipped by intervening boxes=]
 	must be checked after [=updating content relevancy for a document=]
@@ -2687,6 +2690,8 @@ Significant changes since the <a href="https://www.w3.org/TR/2025/WD-css-anchor-
 
 * Clarify positoin fallback interaction with transitions and animation.
 	(<a href="https://github.com/w3c/csswg-drafts/issues/13048">Issue 13048</a>)
+* Clarify that intersection must be non-zero (when anchor box is non-zero) for ''anchors-visible''.
+	(<a href="https://github.com/w3c/csswg-drafts/issues/13176">Issue 13176</a>)
 
 Significant changes since the <a href="https://www.w3.org/TR/2025/WD-css-anchor-position-1-20251007/">7 October 2025 Working Draft</a>: