Merge jqhtml class naming rules, add BEM child class check

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Co-Authored-By: Claude <noreply@anthropic.com>

app/RSpade/man/scss.txt

@@ -285,6 +285,40 @@ HOW IT WORKS
     2. It matches a valid Component subclass or Blade @rsx_id
     3. The filename matches the associated file
 
+BEM CHILD CLASSES
+
+    When using BEM notation inside component SCSS, child element class
+    names must preserve the component's exact PascalCase class name as
+    the prefix. Do NOT convert to kebab-case.
+
+    The SCSS nesting syntax compiles &__element to the parent selector
+    plus __element. Since the parent is .Component_Name, the result is
+    .Component_Name__element - and HTML must use that exact class.
+
+    Correct:
+
+        // SCSS
+        .DataGrid_Kanban {
+            &__loading { ... }
+            &__board { ... }
+            &__column { ... }
+        }
+
+        // HTML (jqhtml template)
+        <div class="DataGrid_Kanban__loading">
+        <div class="DataGrid_Kanban__board">
+        <div class="DataGrid_Kanban__column">
+
+    Wrong:
+
+        // HTML - kebab-case does NOT match compiled CSS
+        <div class="datagrid-kanban__loading">  // No styles applied!
+        <div class="datagrid-kanban__board">    // No styles applied!
+
+    This is a common mistake when following general web conventions where
+    BEM uses kebab-case. In RSX, component class names are PascalCase,
+    so BEM children must also be PascalCase.
+
 NO EXEMPTIONS
 
     There are NO exemptions to this rule for files in rsx/app/ or