feat: focus-within drives the tree pane's rim

Leaf clicks hand ctx focus to the inline value editor, which killed the
tree's focus rim the same frame it lit. The rim now reflects focus-within
the tree pane: lit unless focus sits in the raw editor, the File menu, or
nowhere — synced after every input dispatch. The dead-space unfocus sweep
also clears ctx.focused_widget, which it previously left stale.

Co-Authored-By: Claude Fable 5 <[email protected]>

 src/main.rs | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/src/main.rs b/src/main.rs
index 2dfd4be..462dd3e 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -516,6 +516,20 @@ impl DataEditorApp {
         self.rebuild_tree();
     }
 
+    /// Focus-within for the tree pane's rim: the inline value editors float over
+    /// tree rows and take ctx focus from the TreeList when a leaf is clicked, but
+    /// they are visually part of the tree pane — the rim stays lit for any of
+    /// them (and the tree's own search/rename boxes). It goes out only when focus
+    /// genuinely leaves the pane: the raw editor, the File menu, or nothing.
+    /// Called after every input dispatch (the only places focus moves).
+    fn sync_tree_focus_rim(&mut self) {
+        let ui = &self.ui_context;
+        let outside = !ui.has_focus()
+            || ui.is_focused_id(self.raw_json_editor.id())
+            || ui.is_focused_id(self.btn_open.id());
+        self.tree_list.focused = !outside;
+    }
+
     fn sync_preview_selection(&mut self) {
         if let Some(idx) = self.selected_key_idx {
             if idx < self.flat_keys.len() {
@@ -1640,6 +1654,7 @@ impl Application for DataEditorApp {
             if state == ElementState::Pressed {
                 if self.split.press(px, py) {
                     self.ui_context.clear_focus();
+                    self.sync_tree_focus_rim();
                     *needs_rebuild = true;
                     self.needs_rebuild = true;
                     return None;
@@ -1943,10 +1958,14 @@ impl Application for DataEditorApp {
                 self.selected_choice_editor.unfocus();
                 self.selected_keybind_editor.unfocus();
                 self.tree_list.unfocus();
+                // The manual unfocus sweep above leaves ctx.focused_widget stale;
+                // clear it so focus-derived state (the tree rim) sees reality.
+                self.ui_context.clear_focus();
                 changed = true;
             }
         }
 
+        self.sync_tree_focus_rim();
         if changed {
             *needs_rebuild = true;
             self.needs_rebuild = true;
@@ -2114,6 +2133,7 @@ impl Application for DataEditorApp {
             }
         }
 
+        self.sync_tree_focus_rim();
         if handled {
             *needs_rebuild = true;
             self.needs_rebuild = true;