LibWeb: Restrict style-derived layout predicates

Move layout predicates that require computed values from Node to
NodeWithStyle. Make their style dependency explicit and remove repeated
runtime checks that treated TextNode as a false result.

Keep generic flow classification on Node because text nodes participate
in flow, while routing styled nodes through the direct implementation.

Author: awesomekling

Libraries/LibWeb/Layout/FormattingContext.cpp

@@ -1802,7 +1802,8 @@ static Optional<CSSPixelRect> compute_inline_containing_block_rect(InlineNode co
         }
 
         for (auto child = node.first_child(); child; child = child->next_sibling()) {
-            if (child->is_absolutely_positioned() || child->is_floating())
+            auto const* child_with_style = as_if<NodeWithStyle>(*child);
+            if (child_with_style && (child_with_style->is_absolutely_positioned() || child_with_style->is_floating()))
                 continue;
             auto const* child_used_values = state.try_get(*child);
             auto child_offset = child_used_values ? offset + child_used_values->content_offset() : offset;

Libraries/LibWeb/Layout/InlineLevelIterator.cpp

@@ -379,7 +379,8 @@ Optional<InlineLevelIterator::Item> InlineLevelIterator::generate_next_item()
         return item;
     }
 
-    if (m_current_node->is_absolutely_positioned()) {
+    auto const& current_node_with_style = as<NodeWithStyle>(*m_current_node);
+    if (current_node_with_style.is_absolutely_positioned()) {
         auto const& node = *m_current_node;
         auto has_unattached_inline_start_edges = m_extra_leading_metrics.has_value()
             && (m_extra_leading_metrics->margin != 0 || m_extra_leading_metrics->border != 0 || m_extra_leading_metrics->padding != 0);
@@ -391,7 +392,7 @@ Optional<InlineLevelIterator::Item> InlineLevelIterator::generate_next_item()
         };
     }
 
-    if (m_current_node->is_floating()) {
+    if (current_node_with_style.is_floating()) {
         auto const& node = *m_current_node;
         skip_to_next();
         return Item {