feat: add SPC w {h,j,k,l} spatial window navigation

Pane focus follows actual screen layout: Artists (left), Albums (top-right),
Tracks (bottom-right). h/l jump between left/right columns, j/k move
between vertically stacked panes in the right column.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/claude-agent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/application/handlers.rs

@@ -28,7 +28,8 @@ impl App {
             }
             AppAction::FocusLeft => self.library.focus_left(),
             AppAction::FocusRight => self.library.focus_right(),
-            AppAction::CycleFocus => self.library.cycle_focus(),
+            AppAction::FocusDown => self.library.focus_down(),
+            AppAction::FocusUp => self.library.focus_up(),
             AppAction::GotoFirst => match self.library.focus {
                 LibraryFocus::Artists => self.library.artist_state.select(Some(0)),
                 LibraryFocus::Albums => self.library.album_state.select(Some(0)),

src/application/library_state.rs

@@ -138,8 +138,9 @@ impl LibraryState {
     pub fn focus_left(&mut self) {
         match self.focus {
             LibraryFocus::Artists => {}
-            LibraryFocus::Albums => self.focus = LibraryFocus::Artists,
-            LibraryFocus::Tracks => self.focus = LibraryFocus::Albums,
+            LibraryFocus::Albums | LibraryFocus::Tracks => {
+                self.focus = LibraryFocus::Artists;
+            }
         }
     }
 
@@ -150,21 +151,20 @@ impl LibraryState {
                     self.focus = LibraryFocus::Albums;
                 }
             }
-            LibraryFocus::Albums => {
-                if self.selected_album().is_some() {
-                    self.focus = LibraryFocus::Tracks;
-                }
-            }
-            LibraryFocus::Tracks => {}
+            LibraryFocus::Albums | LibraryFocus::Tracks => {}
         }
     }
 
-    pub fn cycle_focus(&mut self) {
-        self.focus = match self.focus {
-            LibraryFocus::Artists => LibraryFocus::Albums,
-            LibraryFocus::Albums => LibraryFocus::Tracks,
-            LibraryFocus::Tracks => LibraryFocus::Artists,
-        };
+    pub fn focus_down(&mut self) {
+        if self.focus == LibraryFocus::Albums {
+            self.focus = LibraryFocus::Tracks;
+        }
+    }
+
+    pub fn focus_up(&mut self) {
+        if self.focus == LibraryFocus::Tracks {
+            self.focus = LibraryFocus::Albums;
+        }
     }
 
     fn reset_album_selection(&mut self) {

src/input/action.rs

@@ -5,7 +5,8 @@ pub enum AppAction {
     MoveDown,
     FocusLeft,
     FocusRight,
-    CycleFocus,
+    FocusDown,
+    FocusUp,
     GotoFirst,
     GotoLast,
     HalfPageDown,

src/input/keymap.rs

@@ -11,7 +11,7 @@ pub fn build_normal_keymap() -> KeyTrie<AppAction> {
         .unwrap();
     t.bind_desc("l", AppAction::FocusRight, "focus right")
         .unwrap();
-    t.bind_desc("Tab", AppAction::CycleFocus, "cycle focus")
+    t.bind_desc("Tab", AppAction::FocusRight, "next pane")
         .unwrap();
     t.bind_desc("G", AppAction::GotoLast, "last item").unwrap();
     t.bind_desc("C-d", AppAction::HalfPageDown, "half page down")
@@ -41,6 +41,13 @@ pub fn build_normal_keymap() -> KeyTrie<AppAction> {
             b.bind_desc("p", AppAction::PrevTab, "prev")?;
             Ok(())
         })?;
+        g.group("w", "+window", |w| {
+            w.bind_desc("h", AppAction::FocusLeft, "pane left")?;
+            w.bind_desc("l", AppAction::FocusRight, "pane right")?;
+            w.bind_desc("j", AppAction::FocusDown, "pane down")?;
+            w.bind_desc("k", AppAction::FocusUp, "pane up")?;
+            Ok(())
+        })?;
         g.bind_desc("h", AppAction::ShowHelp, "help")?;
         g.bind_desc("q", AppAction::Quit, "quit")?;
         g.bind_desc("n", AppAction::ToggleNotifications, "notifications")?;