Consolidate play/pause icon logic into PlaybackIcons mapper and PlayStateIcon component

Add Disabled parameter to PlayStateIcon; forward to MudIconButton;
pass Disabled="!IsLoaded" from PlayerControls to match Stop button parity.

DeepDrftPublic.Client/Controls/AudioPlayerBar/AudioPlayerBar.razor

@@ -13,8 +13,7 @@ else
             <MudPaper Elevation="8" Class="player-surface pa-3">
 
                 <div class="player-layout">
-                    <PlayerTransportZone IsPlaying="IsPlaying"
-                                         IsLoaded="IsLoaded"
+                    <PlayerTransportZone IsLoaded="IsLoaded"
                                          IsLoading="IsLoading"
                                          IsStreaming="IsStreaming"
                                          LoadProgress="LoadProgress"

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

@@ -17,8 +17,6 @@ public partial class AudioPlayerBar : ComponentBase, IAsyncDisposable
     private bool IsLoading => PlayerService?.IsLoading ?? false;
     private bool IsStreaming => PlayerService?.CanStartStreaming ?? false;
     private bool IsStreamingMode => PlayerService?.IsStreamingMode ?? false;
-    private bool IsPlaying => PlayerService?.IsPlaying ?? false;
-    private bool IsPaused => PlayerService?.IsPaused ?? false;
     private double? Duration => PlayerService?.Duration;
     private double Volume => PlayerService?.Volume ?? 0;
     private double LoadProgress => PlayerService?.LoadProgress ?? 0;

DeepDrftPublic.Client/Controls/AudioPlayerBar/PlayerControls.razor

@@ -1,9 +1,11 @@
+@namespace DeepDrftPublic.Client.Controls.AudioPlayerBar
+@using DeepDrftPublic.Client.Controls
+
 <MudStack Row="true" AlignItems="AlignItems.Center" Spacing="2">
-    <MudIconButton Icon="@GetPlayIcon()"
+    <PlayStateIcon Size="Size.Large"
                    Color="Color.Primary"
-                   Size="Size.Large"
-                   OnClick="@TogglePlayPause"
-                   Disabled="!IsLoaded"/>
+                   Disabled="!IsLoaded"
+                   OnToggle="@TogglePlayPause"/>
     <MudIconButton Icon="@Icons.Material.Filled.Stop"
                    Color="Color.Primary"
                    Size="Size.Large"

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

@@ -1,16 +1,10 @@
-using Microsoft.AspNetCore.Components;
-using MudBlazor;
+using Microsoft.AspNetCore.Components;
 
 namespace DeepDrftPublic.Client.Controls.AudioPlayerBar;
 
 public partial class PlayerControls : ComponentBase
 {
-    [Parameter] public required bool IsPlaying { get; set; }
     [Parameter] public required bool IsLoaded { get; set; }
     [Parameter] public required EventCallback TogglePlayPause { get; set; }
     [Parameter] public required EventCallback Stop { get; set; }
-    private string GetPlayIcon()
-    {
-        return IsPlaying ? Icons.Material.Filled.Pause : Icons.Material.Filled.PlayArrow;
-    }
 }

DeepDrftPublic.Client/Controls/AudioPlayerBar/PlayerTransportZone.razor

@@ -1,8 +1,7 @@
 @namespace DeepDrftPublic.Client.Controls.AudioPlayerBar
 
 <MudStack Row="true" AlignItems="AlignItems.Center" Spacing="1" Class="@Class">
-    <PlayerControls IsPlaying="IsPlaying"
-                    IsLoaded="IsLoaded"
+    <PlayerControls IsLoaded="IsLoaded"
                     TogglePlayPause="TogglePlayPause"
                     Stop="Stop"/>
     @if (IsLoading && !IsStreaming)

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

@@ -4,7 +4,6 @@ namespace DeepDrftPublic.Client.Controls.AudioPlayerBar;
 
 public partial class PlayerTransportZone : ComponentBase
 {
-    [Parameter] public bool IsPlaying { get; set; }
     [Parameter] public bool IsLoaded { get; set; }
     [Parameter] public bool IsLoading { get; set; }
     [Parameter] public bool IsStreaming { get; set; }

DeepDrftPublic.Client/Controls/PlayStateIcon.razor

@@ -0,0 +1,7 @@
+@namespace DeepDrftPublic.Client.Controls
+
+<MudIconButton Icon="@Icon"
+               Color="Color"
+               Size="Size"
+               Disabled="@Disabled"
+               OnClick="@OnToggle"/>

DeepDrftPublic.Client/Controls/PlayStateIcon.razor.cs

@@ -0,0 +1,62 @@
+using DeepDrftModels.DTOs;
+using DeepDrftPublic.Client.Helpers;
+using DeepDrftPublic.Client.Services;
+using Microsoft.AspNetCore.Components;
+using MudBlazor;
+
+namespace DeepDrftPublic.Client.Controls;
+
+/// <summary>
+/// Renders the play/pause transport glyph for either a specific track or global playback,
+/// reading live state off the cascaded <see cref="IStreamingPlayerService"/>. The icon is
+/// always resolved through <see cref="PlaybackIcons.Resolve"/>.
+/// </summary>
+public partial class PlayStateIcon : ComponentBase, IDisposable
+{
+    [CascadingParameter] public IStreamingPlayerService? PlayerService { get; set; }
+
+    /// <summary>
+    /// When non-null, the icon reflects this track's playback state (active only when it is the
+    /// current track). When null, it reflects global playback state.
+    /// </summary>
+    [Parameter] public TrackDto? Track { get; set; }
+
+    [Parameter] public Size Size { get; set; } = Size.Medium;
+    [Parameter] public Color Color { get; set; } = Color.Primary;
+    [Parameter] public bool Disabled { get; set; } = false;
+    [Parameter] public EventCallback OnToggle { get; set; }
+
+    private IStreamingPlayerService? _subscribedService;
+
+    private bool IsActive => Track is null || PlayerService?.CurrentTrack?.Id == Track.Id;
+    private bool IsPlaying => IsActive && (PlayerService?.IsPlaying ?? false);
+    private bool IsPaused => IsActive && (PlayerService?.IsPaused ?? false);
+
+    private string Icon => PlaybackIcons.Resolve(IsPlaying, IsPaused);
+
+    protected override void OnParametersSet()
+    {
+        // The cascade is IsFixed, so the provider's re-render never reaches us; subscribe to the
+        // multicast side-channel to re-render on every player state change. Reference-guarded so
+        // re-parametering is idempotent. Mirrors AudioPlayerBar / TracksView.
+        if (PlayerService != null && !ReferenceEquals(PlayerService, _subscribedService))
+        {
+            if (_subscribedService != null)
+                _subscribedService.StateChanged -= OnPlayerStateChanged;
+
+            PlayerService.StateChanged += OnPlayerStateChanged;
+            _subscribedService = PlayerService;
+        }
+    }
+
+    private void OnPlayerStateChanged() => InvokeAsync(StateHasChanged);
+
+    public void Dispose()
+    {
+        if (_subscribedService != null)
+        {
+            _subscribedService.StateChanged -= OnPlayerStateChanged;
+            _subscribedService = null;
+        }
+    }
+}

DeepDrftPublic.Client/Helpers/PlaybackIcons.cs

@@ -0,0 +1,14 @@
+using MudBlazor;
+
+namespace DeepDrftPublic.Client.Helpers;
+
+/// <summary>
+/// Single source of truth for mapping playback state to a transport glyph across
+/// DeepDrftPublic.Client. Surfaces that render a play/pause icon call <see cref="Resolve"/>
+/// instead of inlining their own ternary.
+/// </summary>
+public static class PlaybackIcons
+{
+    public static string Resolve(bool isPlaying, bool isPaused)
+        => (isPlaying && !isPaused) ? Icons.Material.Filled.Pause : Icons.Material.Filled.PlayArrow;
+}