fix: seek lower-bound guard and pointer-down callback ordering

AudioPlayer.ts: route seeks below bufferStart to seekBeyondBuffer;
previous missing lower-bound caused clamped playback after first seek.
WaveformSeeker: fire OnSeekStart/OnSeekChange before capturePointer
await to prevent fast-click race that locked _isSeeking true.
Latent: WavOffsetService encodes remaining-only DataSize, overwriting
JS this.duration after seek — not fixed here, scope separately.

DeepDrftPublic.Client/Controls/AudioPlayerBar/WaveformSeeker.razor.cs

@@ -183,12 +183,20 @@ public partial class WaveformSeeker : ComponentBase, IAsyncDisposable
     {
         if (!CanSeek) return;
 
-        // Set seeking state BEFORE the async capturePointer so a fast mobile tap that fires
-        // pointerup before capturePointer returns doesn't miss the commit.
         _isSeeking = true;
         _seekFraction = FractionFromOffset(e.OffsetX);
 
-        // Capture the pointer so a drag that leaves the element keeps tracking until release.
+        // Fire seek-start notifications BEFORE awaiting capturePointer. In Blazor WASM a JS
+        // interop await yields to the browser event loop. A fast click can fire pointerup
+        // during that window: HandlePointerUp runs (OnSeekEnd, _isSeeking = false), then
+        // HandlePointerDown resumes and calls OnSeekStart (_isSeeking stuck true, display
+        // frozen). Notifying first ensures the ordering is always Start → End, never End → Start.
+        if (Duration is not > 0) { _isSeeking = false; return; }
+        await OnSeekStart.InvokeAsync();
+        await OnSeekChange.InvokeAsync(_seekFraction * Duration.Value);
+
+        // Capture AFTER seek-start is notified so a fast pointerup cannot reorder
+        // OnSeekEnd before OnSeekStart in AudioPlayerBar.
         if (_jsModule is not null)
         {
             try
@@ -197,13 +205,9 @@ public partial class WaveformSeeker : ComponentBase, IAsyncDisposable
             }
             catch
             {
-                // Capture is a UX nicety; if it fails the gesture still works within the element bounds.
+                // Capture is a UX nicety; gesture still works within element bounds.
             }
         }
-
-        if (Duration is not > 0) { _isSeeking = false; return; }
-        await OnSeekStart.InvokeAsync();
-        await OnSeekChange.InvokeAsync(_seekFraction * Duration.Value);
     }
 
     private async Task HandlePointerMove(PointerEventArgs e)

DeepDrftPublic/Interop/audio/AudioPlayer.ts

@@ -274,14 +274,18 @@ export class AudioPlayer {
             return { success: false, error: 'Invalid seek position' };
         }
 
-        // Get buffered duration (accounting for playback offset)
+        const bufferStart = this.scheduler.getPlaybackOffset();
-        const bufferedDuration = this.scheduler.getTotalDuration() + this.scheduler.getPlaybackOffset();
+        const bufferEnd = this.scheduler.getTotalDuration() + bufferStart;
 
-        // Check if seeking within buffered content
+        // Position must be within [bufferStart, bufferEnd] to use buffered content.
-        if (position <= bufferedDuration) {
+        // A lower-bound check is required: after a seek-beyond-buffer, bufferStart is
+        // set to the prior seek position. Seeking to a position below bufferStart would
+        // produce a negative bufferRelativePosition in seekWithinBuffer, silently
+        // clamping to position 0 of the offset buffer instead of the requested time.
+        if (position >= bufferStart && position <= bufferEnd) {
             return this.seekWithinBuffer(position);
         } else {
-            // Seeking beyond buffer - signal C# to fetch new stream
+            // Seeking outside buffered window - signal C# to fetch new stream
             return this.seekBeyondBuffer(position);
         }
     }