fix(detector): preserve percent-radius signal when width is missing

parseRadiusToPx("50%", 0) used to return 0, and resolveBorderRadiusPx's
"if (fromComputed !== null) return fromComputed" guard short-circuited
with that 0 before ever consulting longhand / inline / stylesheet
fallbacks. Callers that gate on `> 0` (border-accent-on-rounded and
isCardLike's hasRadius) silently lost findings the old
parseFloat(style.borderRadius) === 50 heuristic happened to keep.

In jsdom this is reachable any time style.width resolves to "auto" or
an empty string — parseFloat yields NaN, the `|| 0` fallback turns it
into 0, and any percent radius collapses to nothing. Real-world cards
with `width: 100%` hit this on every load.

Fix: when widthPx is 0 / missing, return the raw percentage number
instead. The percent-to-px conversion only makes sense with a width
reference; without one, the value still serves as a positive presence
signal for boolean checks. The icon-tile circle exclusion is
unaffected because that rule already gates on `siblingWidth >= 32`.

Caught by Cursor Bugbot on PR #115.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/detect-antipatterns-browser.js

@@ -888,7 +888,12 @@ function resolveGradientStops(el, win) {
 // Parse a single CSS length token to pixels. Accepts "12px", "50%", a
 // shorthand like "12px 4px" (uses the first value), or empty / null.
 // Returns the pixel value, or null when the input is unparseable.
-// Percentages need a `widthPx` reference to convert against.
+// Percentages convert against `widthPx` when one is supplied. Without a
+// usable width (jsdom returns "auto" for many real-world elements,
+// which parseFloat collapses to 0), fall back to the raw percentage
+// number so callers gating on `> 0` (border-accent-on-rounded,
+// isCardLike's hasRadius) still see a positive value, matching the
+// original parseFloat("50%") === 50 behavior.
 function parseRadiusToPx(value, widthPx) {
   if (!value || typeof value !== 'string') return null;
   const trimmed = value.trim();
@@ -896,7 +901,10 @@ function parseRadiusToPx(value, widthPx) {
   const first = trimmed.split(/\s+/)[0];
   const num = parseFloat(first);
   if (Number.isNaN(num)) return null;
-  if (/%$/.test(first)) return (num / 100) * (widthPx || 0);
+  if (/%$/.test(first)) {
+    if (widthPx && widthPx > 0) return (num / 100) * widthPx;
+    return num;
+  }
   return num;
 }
 

src/detect-antipatterns.mjs

@@ -883,7 +883,12 @@ function resolveGradientStops(el, win) {
 // Parse a single CSS length token to pixels. Accepts "12px", "50%", a
 // shorthand like "12px 4px" (uses the first value), or empty / null.
 // Returns the pixel value, or null when the input is unparseable.
-// Percentages need a `widthPx` reference to convert against.
+// Percentages convert against `widthPx` when one is supplied. Without a
+// usable width (jsdom returns "auto" for many real-world elements,
+// which parseFloat collapses to 0), fall back to the raw percentage
+// number so callers gating on `> 0` (border-accent-on-rounded,
+// isCardLike's hasRadius) still see a positive value, matching the
+// original parseFloat("50%") === 50 behavior.
 function parseRadiusToPx(value, widthPx) {
   if (!value || typeof value !== 'string') return null;
   const trimmed = value.trim();
@@ -891,7 +896,10 @@ function parseRadiusToPx(value, widthPx) {
   const first = trimmed.split(/\s+/)[0];
   const num = parseFloat(first);
   if (Number.isNaN(num)) return null;
-  if (/%$/.test(first)) return (num / 100) * (widthPx || 0);
+  if (/%$/.test(first)) {
+    if (widthPx && widthPx > 0) return (num / 100) * widthPx;
+    return num;
+  }
   return num;
 }