fix(app): native iOS text selection in assistant messages via UITextView

Fixes #238
Fixes #648
Refs #21

packages/app/src/components/markdown-text.web.tsx

@@ -0,0 +1,31 @@
+import { useMemo, type ReactNode } from "react";
+import { Text, View, type StyleProp, type TextStyle, type ViewStyle } from "react-native";
+
+interface MarkdownTextSpanProps {
+  style?: StyleProp<TextStyle>;
+  children: ReactNode;
+}
+
+// react-native-web renders Text as <span>/<div> with `user-select: text`
+// already applied via markdownStyleMapping. The web bundle must not import
+// react-native-uitextview: its transitive import of codegenNativeComponent
+// pulls in setUpReactDevTools, which doesn't resolve under Metro's web
+// target in dev mode.
+export function MarkdownTextSpan({ style, children }: MarkdownTextSpanProps) {
+  return <Text style={style}>{children}</Text>;
+}
+
+interface MarkdownParagraphViewProps {
+  paragraphStyle: ViewStyle;
+  children: ReactNode;
+}
+
+const MARKDOWN_PARAGRAPH_RESET: ViewStyle = { marginBottom: 0 };
+
+// Same shape as Android — paragraph is a View so block-level children (images)
+// keep their natural layout. Web text selection already spans nested inline
+// elements via CSS user-select, so no UITextView equivalent is needed.
+export function MarkdownParagraphView({ paragraphStyle, children }: MarkdownParagraphViewProps) {
+  const style = useMemo(() => [paragraphStyle, MARKDOWN_PARAGRAPH_RESET], [paragraphStyle]);
+  return <View style={style}>{children}</View>;
+}