fix(ui): wrap "Add to chat" selections in md fenced blocks (#641) (#684)

packages/ui/src/components/chat/message/TextSelectionMenu.tsx
  - What: Wrap selectedText in ```md fenced block before appending to composer.
  - Why: Selections were appended as raw inline text with no visual distinction.

packages/ui/src/components/chat/ChatInput.tsx
  - What: Replace trimEnd()/trim() + single-space join with raw prev + \n\n separator in append branch.
  - Why: Existing composer newlines were being destroyed and multiple appends ran together.

packages/ui/src/components/session/ProjectNotesTodoPanel.tsx
  - What: Wrap todoText in ```md fenced block before appending to composer.
  - Why: Todo text sent to current session should have the same fenced formatting.

packages/ui/src/components/chat/ChatInput.tsx

@@ -589,11 +589,9 @@ export const ChatInput: React.FC<ChatInputProps> = ({ onOpenSettings, scrollToBo
             if (pending?.text) {
                 if (pending.mode === 'append') {
                     setMessage((prev) => {
-                        const next = pending.text.trim();
+                        if (!pending.text) return prev;
-                        if (!next) return prev;
+                        if (!prev.trim()) return pending.text;
-                        const base = prev.trimEnd();
+                        return `${prev}\n\n${pending.text}`;
-                        if (!base.trim()) return next;
-                        return `${base} ${next}`;
                     });
                 } else {
                     setMessage(pending.text);

packages/ui/src/components/chat/message/TextSelectionMenu.tsx

@@ -249,7 +249,8 @@ export const TextSelectionMenu: React.FC<TextSelectionMenuProps> = ({ containerR
   const handleAddToChat = React.useCallback(() => {
     if (!selectedText) return;
 
-    setPendingInputText(selectedText, 'append');
+    const fenced = `\`\`\`md\n${selectedText}\n\`\`\``;
+    setPendingInputText(fenced, 'append');
     
     hideMenu();
     

packages/ui/src/components/session/ProjectNotesTodoPanel.tsx

@@ -192,7 +192,8 @@ export const ProjectNotesTodoPanel: React.FC<ProjectNotesTodoPanelProps> = ({
         return;
       }
       routeToChat();
-      setPendingInputText(todoText, 'append');
+      const fenced = `\`\`\`md\n${todoText}\n\`\`\``;
+      setPendingInputText(fenced, 'append');
       toast.success('Todo sent to current session');
       onActionComplete?.();
     },