fix: use preprocessMarkdown for parsing hashtags and item mentions

The @tiptap/markdown extension doesn't automatically parse custom
markdown syntax like [@Label](/item/id). We need to preprocess the
markdown before loading it into the editor to convert these patterns
to HTML spans that the extensions' parseHTML handlers can recognize.

- RichTextEditor: preprocess defaultValue before loading
- TextView: preprocess innerText before loading

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

lib/src/Components/Map/Subcomponents/ItemPopupComponents/TextView.tsx

@@ -10,6 +10,7 @@ import { useItems } from '#components/Map/hooks/useItems'
 import { useTags } from '#components/Map/hooks/useTags'
 import { Hashtag, ItemMention, VideoEmbed } from '#components/TipTap/extensions'
 import {
+  preprocessMarkdown,
   removeMarkdownSyntax,
   truncateMarkdown,
 } from '#components/TipTap/utils/preprocessMarkdown'
@@ -79,8 +80,8 @@ export const TextView = ({
         }),
         VideoEmbed,
       ],
-      content: innerText,
-      contentType: 'markdown',
+      // Preprocess markdown to convert hashtags and item mentions to HTML
+      content: preprocessMarkdown(innerText),
       editable: false,
       editorProps: {
         attributes: {
@@ -93,7 +94,7 @@ export const TextView = ({
 
   // Update content when text changes
   useEffect(() => {
-    editor.commands.setContent(innerText, { contentType: 'markdown' })
+    editor.commands.setContent(preprocessMarkdown(innerText))
   }, [editor, innerText])
 
   // Handle link clicks for internal navigation