fix: change split-down shortcut to Alt+S to avoid system conflict

- Change split-down from Alt+Shift+D to Alt+S (Alt+Shift is Windows
  keyboard layout switch shortcut)
- Use event.code for keyboard-layout-independent key detection
- Add red theme to dark theme scrollbar selectors
- Add red-themed scrollbar styling with dark red colors
- Tone down white/bright colors in red terminal theme

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/app/src/config/terminal-themes.ts

@@ -334,26 +334,26 @@ const synthwaveTheme: TerminalTheme = {
 // Red theme - Dark theme with red accents
 const redTheme: TerminalTheme = {
   background: "#1a0a0a",
-  foreground: "#e0d0d0",
+  foreground: "#c8b0b0",
   cursor: "#ff4444",
   cursorAccent: "#1a0a0a",
   selectionBackground: "#5a2020",
   black: "#2a1010",
   red: "#ff4444",
-  green: "#88cc88",
-  yellow: "#ffcc66",
-  blue: "#7799cc",
-  magenta: "#cc6699",
-  cyan: "#66aaaa",
-  white: "#e0d0d0",
+  green: "#6a9a6a",
+  yellow: "#ccaa55",
+  blue: "#6688aa",
+  magenta: "#aa5588",
+  cyan: "#558888",
+  white: "#b0a0a0",
   brightBlack: "#6a4040",
   brightRed: "#ff6666",
-  brightGreen: "#aaddaa",
-  brightYellow: "#ffdd88",
-  brightBlue: "#99bbdd",
-  brightMagenta: "#dd88bb",
-  brightCyan: "#88cccc",
-  brightWhite: "#fff0f0",
+  brightGreen: "#88bb88",
+  brightYellow: "#ddbb66",
+  brightBlue: "#88aacc",
+  brightMagenta: "#cc77aa",
+  brightCyan: "#77aaaa",
+  brightWhite: "#d0c0c0",
 };
 
 // Theme mapping