fix: pass onLinkPress to SelectableMarkdownText in FileMarkdownPreview

On iOS, FileMarkdownPreview rendered SelectableMarkdownText without
onLinkPress, causing link taps to fall through to raw Linking.openURL
instead of going through tryOpenExternalUrl. This left the iOS path
without ExternalUrlOpenError logging and with unhandled rejections.

Pass an onLinkPress callback that routes through tryOpenExternalUrl,
consistent with how ThreadFeed already handles native markdown links.

Author: cursoragent

apps/mobile/src/features/files/FileMarkdownPreview.tsx

@@ -1,4 +1,4 @@
-import { useMemo } from "react";
+import { useCallback, useMemo } from "react";
 import {
   Markdown,
   type CustomRenderers,
@@ -144,12 +144,19 @@ function useMarkdownPreviewStyles(): MarkdownPreviewStyles {
 
 export function FileMarkdownPreview(props: { readonly markdown: string }) {
   const styles = useMarkdownPreviewStyles();
+  const onLinkPress = useCallback((href: string) => {
+    void tryOpenExternalUrl(href, "markdown-link");
+  }, []);
 
   return (
     <ScrollView className="flex-1 bg-card" contentContainerStyle={{ padding: 18 }}>
       <View className="mx-auto w-full max-w-[760px]">
         {hasNativeSelectableMarkdownText() ? (
-          <SelectableMarkdownText markdown={props.markdown} textStyle={styles.nativeTextStyle} />
+          <SelectableMarkdownText
+            markdown={props.markdown}
+            textStyle={styles.nativeTextStyle}
+            onLinkPress={onLinkPress}
+          />
         ) : (
           <Markdown
             options={{ gfm: true }}