feat(tui): add Ctrl+↑/↓ shortcuts to resize chat/thinking split

- Update help UI to show “Ctrl+↑/↓ → resize chat/thinking split”.
- Introduce `ensure_ratio_bounds` and `nudge_ratio` on `LayoutNode` to clamp and adjust split ratios.
- Ensure vertical split favors the thinking panel when it becomes focused.
- Add `adjust_vertical_split` method in `ChatApp` and handle Ctrl+↑/↓ in normal mode to modify the split and update status messages.

crates/owlen-tui/src/chat_app.rs

@@ -2407,6 +2407,12 @@ impl ChatApp {
         } else if !order.contains(&self.focused_panel) {
             self.focused_panel = order[0];
         }
+        if let FocusedPanel::Thinking = self.focused_panel {
+            // Ensure the vertical split favours thinking panel if chat collapsed entirely
+            if let Some(tab) = self.workspace_mut().active_tab_mut() {
+                tab.root.ensure_ratio_bounds();
+            }
+        }
     }
 
     pub fn cycle_focus_forward(&mut self) {
@@ -2461,6 +2467,12 @@ impl ChatApp {
         configure_textarea_defaults(&mut self.textarea);
     }
 
+    pub fn adjust_vertical_split(&mut self, delta: f32) {
+        if let Some(tab) = self.workspace_mut().active_tab_mut() {
+            tab.root.nudge_ratio(delta);
+        }
+    }
+
     async fn process_slash_submission(&mut self) -> Result<SlashOutcome> {
         let raw = self.controller.input_buffer().text().to_string();
         if raw.trim().is_empty() {
@@ -4169,6 +4181,16 @@ impl ChatApp {
                         key.code,
                         KeyCode::Right | KeyCode::Char('l') | KeyCode::Char('L')
                     );
+                let is_resize_up = key.modifiers.contains(KeyModifiers::CONTROL)
+                    && matches!(
+                        key.code,
+                        KeyCode::Up | KeyCode::Char('k') | KeyCode::Char('K')
+                    );
+                let is_resize_down = key.modifiers.contains(KeyModifiers::CONTROL)
+                    && matches!(
+                        key.code,
+                        KeyCode::Down | KeyCode::Char('j') | KeyCode::Char('J')
+                    );
 
                 if is_reveal_active && matches!(self.mode, InputMode::Normal) {
                     self.reveal_active_file();
@@ -4208,6 +4230,21 @@ impl ChatApp {
                     return Ok(AppState::Running);
                 }
 
+                if (is_resize_up || is_resize_down) && matches!(self.mode, InputMode::Normal) {
+                    let delta = if is_resize_up { -0.05 } else { 0.05 };
+                    self.adjust_vertical_split(delta);
+                    self.status = format!(
+                        "Vertical split adjusted ({})",
+                        if delta.is_sign_positive() {
+                            "down"
+                        } else {
+                            "up"
+                        }
+                    );
+                    self.error = None;
+                    return Ok(AppState::Running);
+                }
+
                 if is_symbol_search_key && matches!(self.mode, InputMode::Normal) {
                     self.set_input_mode(InputMode::SymbolSearch);
                     self.symbol_search.clear_query();

crates/owlen-tui/src/state/workspace.rs

@@ -85,6 +85,31 @@ pub enum LayoutNode {
 }
 
 impl LayoutNode {
+    pub fn ensure_ratio_bounds(&mut self) {
+        match self {
+            LayoutNode::Split {
+                ratio,
+                first,
+                second,
+                ..
+            } => {
+                *ratio = ratio.clamp(0.1, 0.9);
+                first.ensure_ratio_bounds();
+                second.ensure_ratio_bounds();
+            }
+            LayoutNode::Leaf(_) => {}
+        }
+    }
+
+    pub fn nudge_ratio(&mut self, delta: f32) {
+        match self {
+            LayoutNode::Split { ratio, .. } => {
+                *ratio = (*ratio + delta).clamp(0.1, 0.9);
+            }
+            LayoutNode::Leaf(_) => {}
+        }
+    }
+
     fn replace_leaf(&mut self, target: PaneId, replacement: LayoutNode) -> bool {
         match self {
             LayoutNode::Leaf(id) => {

crates/owlen-tui/src/ui.rs

@@ -3070,6 +3070,7 @@ fn render_help(frame: &mut Frame<'_>, app: &ChatApp) {
             Line::from("  :h, :help     → open help from command mode"),
             Line::from("  :files, :explorer → toggle files panel"),
             Line::from("  Ctrl+←/→      → resize files panel"),
+            Line::from("  Ctrl+↑/↓      → resize chat/thinking split"),
         ],
         1 => vec![
             // Editing
@@ -3183,6 +3184,7 @@ fn render_help(frame: &mut Frame<'_>, app: &ChatApp) {
             Line::from("  F1 or ?           → toggle help overlay"),
             Line::from("  :files, :explorer → toggle files panel"),
             Line::from("  Ctrl+←/→          → resize files panel"),
+            Line::from("  Ctrl+↑/↓          → resize chat/thinking split"),
             Line::from("  :quit              → quit application"),
             Line::from("  Ctrl+C twice       → quit application"),
             Line::from("  :reload            → reload configuration and themes"),