fix(titlebar): hide traffic-light glyphs until hover (#243)

* fix(titlebar): hide traffic-light glyphs until hover

The lucide Minus/Square/X icons at 9×9 with stroke-width 2.5 looked
chunky at all times — especially the Square for maximize. Match real
macOS behaviour: glyphs fade in only when the controls group is hovered
(or a button is keyboard-focused).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* fix(titlebar): drop traffic-light glyphs entirely, add coloured hover glow

Following review feedback: even on-hover the lucide glyphs at 9×9
weren't pleasant. Remove them outright and signal hover with a soft
coloured glow matching each button (red/yellow/green) plus a subtle
brightness lift. Keyboard focus uses a white outer ring for accessibility.

- TitleBar.tsx: remove lucide imports + icon children, add aria-label
- layout.css: drop svg sizing rules, add per-variant box-shadow hover,
  add focus-visible ring, transition box-shadow

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Psychotoxical <dev@psysonic.app>
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/components/TitleBar.tsx

@@ -1,6 +1,5 @@
 import React from 'react';
 import { getCurrentWindow } from '@tauri-apps/api/window';
-import { X, Minus, Square } from 'lucide-react';
 import { usePlayerStore } from '../store/playerStore';
 
 export default function TitleBar() {
@@ -27,25 +26,22 @@ export default function TitleBar() {
           onClick={() => win.minimize()}
           data-tooltip="Minimize"
           data-tooltip-pos="bottom"
-        >
-          <Minus size={10} />
-        </button>
+          aria-label="Minimize"
+        />
         <button
           className="titlebar-btn titlebar-btn-maximize"
           onClick={() => win.toggleMaximize()}
           data-tooltip="Maximize"
           data-tooltip-pos="bottom"
-        >
-          <Square size={9} />
-        </button>
+          aria-label="Maximize"
+        />
         <button
           className="titlebar-btn titlebar-btn-close"
           onClick={() => win.close()}
           data-tooltip="Close"
           data-tooltip-pos="bottom"
-        >
-          <X size={12} />
-        </button>
+          aria-label="Close"
+        />
       </div>
     </div>
   );