feat(tui): results across the top, with panes you can hide, zoom and Tab through

The results pane now has the whole width, where a long file name needs it,
and Searches, Downloads and Info share the row underneath. Tab and Shift-Tab
walk the panes, z zooms the focused one to the window, w hides it so the
others widen, and its number brings it back. Every list takes the same
navigation keys, the shortcuts bar wraps instead of cutting keys off, and ?
lists every key by pane, scrolling on a short terminal.

Follows up on #55.

soulseek-rs/src/ui/main_tui/search.rs

@@ -231,8 +231,8 @@ impl MainTui {
         self.state.results_table_state.select(Some(0));
         self.state.results_name_offset = 0;
 
-        // Switch focus to Results pane
-        self.state.focused_pane = FocusedPane::Results;
+        // Switch focus to Results pane, bringing it back if it was hidden
+        self.state.focus_pane(FocusedPane::Results);
 
         let client = self.client.clone();
         let timeout = self.search_timeout;