Fix rtl text rendering (#21382)

* Fix Arabic RTL text rendering in web UI

- Add dir='auto' attributes to markdown containers and blocks
- Implement post-processing to add dir='auto' to all text elements
- Replace directional CSS properties with logical properties for proper RTL list alignment
- Ensure bidirectional text support for mixed Arabic/English content

* Clean up commented duplicate function

Remove the commented-out duplicate transformMdastNode function
that was left over from refactoring.

* Fix Arabic RTL text rendering in web UI

- Add dir='auto' attributes to markdown containers and blocks
- Implement post-processing to add dir='auto' to all text elements
- Replace directional CSS properties with logical properties for proper RTL list alignment
- Minor code formatting improvements

This ensures bidirectional text support for mixed Arabic/English content in the llama.cpp web UI.

* Implement rehype plugin for comprehensive RTL text support

- Add rehypeRtlSupport plugin that applies dir='auto' to all elements with children
- Replace DOMParser-based approach with efficient HAST tree processing
- Remove hardcoded element lists for better maintainability
- Ensure proper bidirectional text rendering for mixed RTL/LTR content

* Fix RTL text rendering with rehype plugin and cleanup

* fix: prettier formatting

tools/server/webui/src/lib/markdown/rehype-rtl-support.ts

@@ -0,0 +1,28 @@
+/**
+ * Rehype plugin to provide comprehensive RTL support by adding dir="auto"
+ * to all text-containing elements.
+ *
+ * This operates directly on the HAST tree, ensuring that all elements
+ * (including those not in a predefined list) receive the attribute.
+ */
+
+import type { Plugin } from 'unified';
+import type { Root, Element } from 'hast';
+import { visit } from 'unist-util-visit';
+
+/**
+ * Rehype plugin to add dir="auto" to all elements that have children.
+ * This provides bidirectional text support for mixed RTL/LTR content.
+ */
+export const rehypeRtlSupport: Plugin<[], Root> = () => {
+	return (tree: Root) => {
+		visit(tree, 'element', (node: Element) => {
+			if (node.children && node.children.length > 0) {
+				node.properties = {
+					...node.properties,
+					dir: 'auto'
+				};
+			}
+		});
+	};
+};