Fix race condition with autoCenter/autoScroll during loadBlob (#4187)

Fixed a race condition where autoScroll and autoCenter would sometimes
cause the scroll position to jump to the beginning when loading a blob.

The issue occurred when renderProgress was called while the audio data
was still being loaded/decoded (duration temporarily 0 or invalid), which
triggered scrollIntoView to scroll to position 0.

The fix adds a guard to only call scrollIntoView when valid audio data
exists with a duration > 0, preventing the race condition.

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

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

Author: GitHub Copilot

.beads/issues.jsonl

@@ -0,0 +1 @@
+{"id":"wavesurfer.js-pgw","title":"Fix race condition with autoCenter/autoScroll during loadBlob","description":"","status":"closed","priority":2,"issue_type":"bug","created_at":"2025-12-04T20:44:48.179843+01:00","updated_at":"2025-12-04T20:48:52.196792+01:00","closed_at":"2025-12-04T20:48:52.196792+01:00"}

src/renderer.ts

@@ -725,7 +725,8 @@ class Renderer extends EventEmitter<RendererEvents> {
       ? `translateX(-${progress * this.options.cursorWidth}px)`
       : ''
 
-    if (this.isScrollable && this.options.autoScroll) {
+    // Only scroll if we have valid audio data to prevent race conditions during loading
+    if (this.isScrollable && this.options.autoScroll && this.audioData && this.audioData.duration > 0) {
       this.scrollIntoView(progress, isPlaying)
     }
   }