fix: refresh cached diff colors for external theme updates

src/tui.rs

@@ -269,6 +269,7 @@ struct BufferViewports {
     parked: BTreeMap<usize, PaneViewport>,
     rects: Vec<(usize, Rect)>,
     theme: Option<ThemeColors>,
+    diff_visible: bool,
 }
 
 #[derive(Default)]
@@ -550,6 +551,16 @@ impl BufferViewports {
         } else {
             draw_overlays(frame, editor, area, self.panels.caret, &mut self.panels);
         }
+        self.diff_visible = self
+            .panels
+            .diff
+            .iter()
+            .chain(
+                self.parked
+                    .values()
+                    .filter_map(|pane| pane.panels.diff.as_ref()),
+            )
+            .any(|geometry| geometry.viewport.is_some());
     }
 
     fn draw_session(&mut self, frame: &mut Frame, session: &mut EditorSession) {
@@ -785,9 +796,12 @@ pub fn run(session: &mut EditorSession) -> io::Result<()> {
                 redraw = false;
             }
             // Start the reply deadline after painting, not before expensive syntax initialization.
-            if query_theme {
-                colors.query(&mut output, Instant::now())?;
-                query_theme = false;
+            if query_theme || viewports.diff_visible {
+                let now = Instant::now();
+                if query_theme || colors.refresh_due(now) {
+                    colors.query(&mut output, now)?;
+                    query_theme = false;
+                }
             }
             let input = if let Some(input) = pending.take() {
                 input