feat: Stream Now instant-play of a random track from the nav button

DeepDrftPublic.Client/Layout/DeepDrftMenu.razor

@@ -16,7 +16,20 @@
         </ul>
 
         <div class="dd-nav-actions">
-            <a href="/tracks" class="dd-nav-cta">Stream Now &#9654;</a>
+            <button type="button"
+                    class="dd-nav-cta"
+                    disabled="@_streamLoading"
+                    aria-busy="@_streamLoading.ToString().ToLowerInvariant()"
+                    @onclick="StreamNow">
+                @if (_streamLoading)
+                {
+                    <span>Finding a track&#8230;</span>
+                }
+                else
+                {
+                    <span>Stream Now &#9654;</span>
+                }
+            </button>
             @* <button type="button" *@
             @*         class="dd-nav-toggle" *@
             @*         aria-label="Toggle dark mode" *@
@@ -25,6 +38,11 @@
             @*     @((MarkupString)DarkLightModeIconSvg) *@
             @* </button> *@
         </div>
+
+        @if (_streamMessage is not null)
+        {
+            <p class="dd-nav-stream-message" role="status">@_streamMessage</p>
+        }
     </nav>
 </div>
 
@@ -60,15 +78,37 @@
                     </li>
                 }
                 <li>
-                    <a href="/tracks" class="dd-nav-cta" @onclick="CloseMobileMenu">Stream Now &#9654;</a>
+                    <button type="button"
+                            class="dd-nav-cta"
+                            disabled="@_streamLoading"
+                            aria-busy="@_streamLoading.ToString().ToLowerInvariant()"
+                            @onclick="StreamNowMobile">
+                        @if (_streamLoading)
+                        {
+                            <span>Finding a track&#8230;</span>
+                        }
+                        else
+                        {
+                            <span>Stream Now &#9654;</span>
+                        }
+                    </button>
                 </li>
             </ul>
         }
+
+        @if (_streamMessage is not null)
+        {
+            <p class="dd-nav-stream-message" role="status">@_streamMessage</p>
+        }
     </nav>
 </div>
 
+@implements IDisposable
+
 @code {
     [Inject] public required DarkModeCookieService DarkModeCookieService { get; set; }
+    [Inject] public required ITrackDataService TrackData { get; set; }
+    [CascadingParameter] public IStreamingPlayerService? PlayerService { get; set; }
 
     // Elevation is vestigial under the frosted-glass design but kept on the parameter
     // surface so MainLayout's <DeepDrftMenu Elevation="..."> call site stays intact.
@@ -77,6 +117,99 @@
     [Parameter] public required EventCallback<bool> IsDarkModeChanged { get; set; }
     
     private bool _mobileMenuOpen;
+    private bool _streamLoading;
+    private string? _streamMessage;
+    private CancellationTokenSource? _messageCts;
+
+    private const string EmptyLibraryMessage = "No tracks yet — check back soon.";
+    private const string FetchFailedMessage = "Couldn't reach the library — try again.";
+
+    private Task StreamNow() => StreamNowCore(closeMobileMenu: false);
+
+    private Task StreamNowMobile() => StreamNowCore(closeMobileMenu: true);
+
+    private async Task StreamNowCore(bool closeMobileMenu)
+    {
+        // Re-entrancy guard: the button is disabled while loading, but guard in code too so a
+        // double-dispatch can never start two concurrent streams.
+        if (_streamLoading) return;
+
+        _streamLoading = true;
+        _streamMessage = null;
+
+        // Warm the AudioContext FIRST, inside the gesture's call stack and before the network
+        // await below. Safari only lets a suspended AudioContext resume while the originating
+        // user gesture is still active; awaiting GetRandomTrack() first would consume the gesture
+        // and leave playback silently refused. PlayerService is null only outside the
+        // AudioPlayerProvider cascade (it should always be present in the public layout).
+        var warmTask = PlayerService?.WarmAudioContext() ?? Task.CompletedTask;
+
+        try
+        {
+            await warmTask;
+            var result = await TrackData.GetRandomTrack();
+
+            if (!result.Success)
+            {
+                ShowTransientMessage(FetchFailedMessage);
+                return;
+            }
+
+            if (result.Value is not { } track)
+            {
+                ShowTransientMessage(EmptyLibraryMessage);
+                return;
+            }
+
+            if (closeMobileMenu)
+                _mobileMenuOpen = false;
+
+            if (PlayerService is not null)
+                await PlayerService.SelectTrackStreaming(track);
+        }
+        catch (Exception)
+        {
+            ShowTransientMessage(FetchFailedMessage);
+        }
+        finally
+        {
+            _streamLoading = false;
+        }
+    }
+
+    private void ShowTransientMessage(string message)
+    {
+        _streamMessage = message;
+
+        // Cancel any in-flight clear timer so the newest message gets its full display window.
+        _messageCts?.Cancel();
+        _messageCts?.Dispose();
+        _messageCts = new CancellationTokenSource();
+        var token = _messageCts.Token;
+
+        _ = ClearMessageAfterDelayAsync(token);
+    }
+
+    private async Task ClearMessageAfterDelayAsync(CancellationToken token)
+    {
+        try
+        {
+            await Task.Delay(TimeSpan.FromSeconds(4), token);
+        }
+        catch (TaskCanceledException)
+        {
+            return;
+        }
+
+        _streamMessage = null;
+        await InvokeAsync(StateHasChanged);
+    }
+
+    public void Dispose()
+    {
+        _messageCts?.Cancel();
+        _messageCts?.Dispose();
+    }
 
     protected override async Task OnAfterRenderAsync(bool firstRender)
     {