fix scroll height and prose line breaks in rich output

- Loader delegate: set explicit height from item.implicitHeight so
  ListView can calculate correct contentHeight for scrolling
- Prose sub-blocks: escape HTML, convert newlines to <br> before
  linkifying paths (RichText ignores bare newlines)

gui/main.qml

@@ -393,6 +393,7 @@ ApplicationWindow {
 
                         delegate: Loader {
                             width: chatList.width
+                            height: item ? item.implicitHeight : 0
                             property var block: model
                             sourceComponent: {
                                 switch (blockType) {
@@ -499,8 +500,13 @@ ApplicationWindow {
     // --- Chat block delegates ---
 
     function linkifyPaths(text) {
+        // Escape HTML entities first
+        let escaped = text.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;')
+        // Convert newlines to <br>
+        escaped = escaped.replace(/\n/g, '<br>')
         // Match /absolute/path or /absolute/path:line
-        return text.replace(/(\/[\w\-.\/]+(?::\d+)?)/g, '<a href="file://$1">$1</a>')
+        escaped = escaped.replace(/(\/[\w\-.\/]+(?::\d+)?)/g, '<a href="file://$1">$1</a>')
+        return escaped
     }
 
     Component {