Use inline WYSIWYG markdown editor for long text messages

Desktop: replace the Write/Preview tab toggle in the compose card with
MDXEditor, an inline WYSIWYG that renders markdown as you type (Obsidian/
Notion feel) and round-trips plain markdown, matching how particle content
is stored. Immersive mode is unchanged — short, plain notes still get the
centered large-type textarea, and ⌘+M still drops into the rich editor.
Shortcut handling moves to the capture phase so ⌘+Enter / Esc win over the
editor's own key handling.

Mobile: render markdown on the display side via react-native-marked's
useMarkdown hook (no FlatList, so it nests cleanly in the existing
ScrollView). Mirrors desktop's immersive-vs-card logic: short plain notes
stay centered; anything with markdown renders formatted instead of showing
raw syntax. Composer stays plain text.

https://claude.ai/code/session_019DU6V5z6Nr4Vu7b1fBDnq4

js/mobile/package.json

@@ -13,6 +13,10 @@
   },
   "packageManager": "[email protected]",
   "dependencies": {
+    "@config-plugins/react-native-webrtc": "^12.0.0",
+    "@livekit/react-native": "^2.7.5",
+    "@livekit/react-native-expo-plugin": "^1.0.2",
+    "@livekit/react-native-webrtc": "^144.1.0",
     "@react-native-async-storage/async-storage": "2.2.0",
     "@react-navigation/native": "^7.0.14",
     "@react-navigation/native-stack": "^7.2.0",
@@ -30,16 +34,13 @@
     "expo-status-bar": "~3.0.9",
     "expo-video": "~3.0.10",
     "firebase": "^12.10.0",
-    "@config-plugins/react-native-webrtc": "^12.0.0",
-    "@livekit/react-native": "^2.7.5",
-    "@livekit/react-native-expo-plugin": "^1.0.2",
-    "@livekit/react-native-webrtc": "^144.1.0",
     "livekit-client": "^2.15.2",
     "lucide-react-native": "^0.575.0",
     "nativewind": "^4.1.23",
     "react": "19.1.0",
     "react-native": "0.81.5",
     "react-native-gesture-handler": "~2.28.0",
+    "react-native-marked": "^8.1.0",
     "react-native-reanimated": "~4.1.1",
     "react-native-safe-area-context": "~5.6.0",
     "react-native-screens": "~4.16.0",