fix(dev-server): preserve nested component named slots

packages/dev-server/src/runtime.ts

@@ -2622,8 +2622,9 @@ function extractSlots(inner: string): { named: Record<string, string>; def: stri
   const named: Record<string, string> = {};
   if (!inner.includes("data-slot=")) return { named, def: inner };
 
-  const SLOT_MOUNT_RE =
-    /<([A-Za-z][A-Za-z0-9-]*)\b([^>]*?\bdata-slot="([A-Za-z0-9_-]+)"[^>]*?)(\/?)>/;
+  // Only direct children belong to this mount. Descendant named slots belong
+  // to their own component (for example a splitter inside a shell's slot).
+  const SLOT_MOUNT_RE = /<([A-Za-z][A-Za-z0-9-]*)\b([^>]*?)(\/?)>/;
   let def = "";
   let i = 0;
   for (;;) {
@@ -2634,11 +2635,16 @@ function extractSlots(inner: string): { named: Record<string, string>; def: stri
     }
     const tagStart = i + m.index;
     def += inner.slice(i, tagStart);
-    const [open, tag, , name, selfClose] = m;
+    const [open, tag, attributes, selfClose] = m;
+    const name = /\bdata-slot="([A-Za-z0-9_-]+)"/.exec(attributes!)?.[1];
     const openEnd = tagStart + open.length;
     const { inner: content, end } =
-      selfClose === "/" ? { inner: "", end: openEnd } : readElementBody(inner, tag!, openEnd);
-    named[name!] = content;
+      selfClose === "/" ||
+      /^(area|base|br|col|embed|hr|img|input|link|meta|param|source|track|wbr)$/i.test(tag!)
+        ? { inner: "", end: openEnd }
+        : readElementBody(inner, tag!, openEnd);
+    if (name) named[name] = content;
+    else def += inner.slice(tagStart, end);
     i = end;
   }
   return { named, def };