fix(svg): also drop single-stop translucent gradient overlays

isAlphaOnlyOverlay required two or more stops, so a one-stop translucent
same-colour gradient — a flat alpha fill, which paint() expands to an
opaque flat fill — still blotted the art beneath it. Treat a single
translucent stop as an overlay too. Also document that nested clip-paths
take the innermost shape (no intersection): this is exact for the Noto set
(no glyph nests a different clip) and any residual overflow stays bounded
by the inline viewBox clip.

Author: DemchaAV

src/main/java/com/demcha/compose/document/svg/SvgGradients.java

@@ -169,9 +169,11 @@ static boolean isAlphaOnlyOverlay(Element gradient, Map<String, Element> all) {
                 stops = stopElements(target);
             }
         }
-        if (stops.size() < 2) {
+        if (stops.isEmpty()) {
             return false;
         }
+        // A single translucent stop is a flat alpha fill — still an overlay we
+        // cannot composite, so it is caught here too (not only two-stop fades).
         Integer rgb = null;
         boolean translucent = false;
         for (Element stop : stops) {

src/main/java/com/demcha/compose/document/svg/SvgIconReader.java

@@ -151,8 +151,11 @@ private static void walk(Element element, double[] transform, Paint inherited, S
             paint = stylize(element, inherited, gradients);
             matrix = compose(transform, element.getAttribute("transform"));
             // A clip-path on this element (or group) clips it and its descendants
-            // to the referenced shape; the innermost clip wins. Resolved in icon
-            // space with the same matrix/box as the geometry it bounds.
+            // to the referenced shape, resolved in icon space with the same
+            // matrix/box as the geometry it bounds. Nested clips are not
+            // intersected — the innermost wins; this is exact for the Noto set
+            // (no glyph nests a different clip inside another) and any residual
+            // overflow is still bounded by the inline viewBox clip at render.
             SvgPath ownClip = resolveClip(element, matrix, box, ids);
             if (ownClip != null) {
                 activeClip = ownClip;

src/test/java/com/demcha/compose/document/svg/SvgIconTest.java

@@ -452,6 +452,23 @@ void monochromeTranslucentGradientOverlayIsDropped() {
         assertThat(icon.layers().get(0).fill().color()).isEqualTo(new java.awt.Color(0, 255, 0));
     }
 
+    @Test
+    void singleStopTranslucentGradientOverlayIsDropped() {
+        // A one-stop translucent gradient is a flat alpha fill — still an overlay
+        // we cannot composite, so it is dropped too (not only two-stop fades).
+        SvgIcon icon = SvgIcon.parse("""
+                <svg viewBox="0 0 10 10">
+                  <radialGradient id="g">
+                    <stop offset="0" style="stop-color:#000000;stop-opacity:0.2"/>
+                  </radialGradient>
+                  <path d="M0 0 H10 V10 Z" fill="#00ff00"/>
+                  <path d="M0 0 H10 V10 Z" fill="url(#g)"/>
+                </svg>
+                """);
+        assertThat(icon.layers()).hasSize(1);
+        assertThat(icon.layers().get(0).fill().color()).isEqualTo(new java.awt.Color(0, 255, 0));
+    }
+
     @Test
     void multiColourTranslucentGradientStillRenders() {
         // A real colour transition (red→blue) is structural even with a