feat(puzzle): add stats completion sound loop and refine glow/timing logic

- Load new `sfx_stats.mp3` audio for puzzle completion stats display
- Increase glow delay from 500ms to 700ms for smoother visual transition
- Fix indentation in edge detection filter and normalize spacing in CSS/style assignments
- Stop and destroy stats sound on overlay cleanup or completion typing finish
- Start looping stats sound when typing puzzle completion stats, ensuring clean lifecycle management

js/scenes/PuzzleScene.js

@@ -108,6 +108,9 @@ class PuzzleScene extends Phaser.Scene {
     if (!this.cache.audio.exists('sfx_grab')) {
       this.load.audio('sfx_grab', 'assets/audio/fx/grab.mp3');
     }
+    if (!this.cache.audio.exists('sfx_stats')) {
+      this.load.audio('sfx_stats', 'assets/audio/fx/stats.mp3');
+    }
 
     // Music track list
     if (!this.cache.json.exists('music_tracks')) {
@@ -1228,7 +1231,7 @@ class PuzzleScene extends Phaser.Scene {
     if (!this._glowingPieceIds) this._glowingPieceIds = new Set();
     if (!this._glowTimers) this._glowTimers = new Map();
 
-    const GLOW_DELAY = 500; // ms a neighbor must stay in range before glow appears
+    const GLOW_DELAY = 700; // ms a neighbor must stay in range before glow appears
     const now = Date.now();
 
     // Track which neighbors are in proximity this frame
@@ -2811,11 +2814,13 @@ class PuzzleScene extends Phaser.Scene {
     const typeNext = () => {
       if (this._completionOverlay === null) {
         clearInterval(cursorBlink);
+        if (this._statsSound) { this._statsSound.stop(); this._statsSound.destroy(); this._statsSound = null; }
         return;
       }
 
       if (lineIdx >= lines.length) {
-        // Done — keep cursor blinking at end
+        // Done — stop stats sound, keep cursor blinking at end
+        if (this._statsSound) { this._statsSound.stop(); this._statsSound.destroy(); this._statsSound = null; }
         return;
       }
 
@@ -2855,7 +2860,9 @@ class PuzzleScene extends Phaser.Scene {
       }
     };
 
-    // Start typing after a short delay
+    // Start stats sound loop and typing after a short delay
+    this._statsSound = this.sound.add('sfx_stats', { loop: true, volume: 0.5 });
+    this._statsSound.play();
     setTimeout(typeNext, 500);
   }