Unify the drop zones into one component

app/MindWork AI Studio/Pages/Chat.razor

@@ -4,7 +4,7 @@
 
 @* The chat is a drop area: a file dropped anywhere in it hangs itself on the composer, which is
    what users are used to. *@
-<DropZoneScope Class="inner-scrolling-context">
+<PathDropZone IsArea="@true" Class="inner-scrolling-context">
     
     <MudStack Row="true" AlignItems="AlignItems.Center" Class="mb-2" StretchItems="StretchItems.Start">
         <MudText Typo="Typo.h3">
@@ -168,4 +168,4 @@
             </MudDrawerContainer>
         </MudDrawer>
     }
-</DropZoneScope>
+</PathDropZone>

app/MindWork AI Studio/Pages/Plugins.razor

@@ -5,8 +5,13 @@
 @attribute [Route(Routes.PLUGINS)]
 
 @* The page is its own drop target: a plugin archive may be dropped anywhere on it, and there is no
-   inner zone to hand that role to. Hence the page owns the scope state instead of reading it. *@
-<DropZoneScope State="@this.dropZoneScope" Class="inner-scrolling-context">
+   inner zone to hand that role to. An area which takes drops itself is that target by definition. *@
+<PathDropZone IsArea="@true"
+              IdPrefix="plugins-page"
+              Class="inner-scrolling-context"
+              Disabled="@(() => !this.CanCatchDroppedFile())"
+              OnPathsDropped="@this.ImportDroppedPluginArchiveAsync"
+              Context="isDropTarget">
     <MudStack Row="true" AlignItems="AlignItems.Center" Class="mb-2">
         <MudText Typo="Typo.h3">
             @T("Plugins")
@@ -26,7 +31,7 @@
     
     <InnerScrolling>
         
-        <MudTable Items="@PluginFactory.AvailablePlugins" Hover="@true" GroupBy="@this.groupConfig" Class="@this.PluginTableClass">
+        <MudTable Items="@PluginFactory.AvailablePlugins" Hover="@true" GroupBy="@this.groupConfig" Class="@PluginTableClass(isDropTarget)">
             <ColGroup>
                 <col style="width: 2em;" />
                 <col style="width: 2.1em; "/>
@@ -155,4 +160,4 @@
             </RowTemplate>
         </MudTable>
     </InnerScrolling>
-</DropZoneScope>
+</PathDropZone>

app/MindWork AI Studio/Pages/Plugins.razor.cs

@@ -42,14 +42,6 @@ public partial class Plugins : MSGComponentBase
     
     private bool isSharingPlugin;
 
-    /// <summary>
-    /// The drop area of this page. The page owns it rather than reading it from a cascading value,
-    /// because a component cannot read what it cascades itself.
-    /// </summary>
-    private readonly DropZoneScopeState dropZoneScope = new($"plugins-page-{Guid.NewGuid():N}");
-
-    private bool isDraggingOverPage;
-
     private const string IMPORT_ICON =
         @"<svg class=""mud-icon-root mud-svg-icon mud-dark-text mud-icon-size-medium"" focusable=""false"" viewBox=""0 0 24 24"" aria-hidden=""true"" role=""img"">
     <path d=""M0 0h24v24H0V0z"" fill=""none""></path>
@@ -61,10 +53,7 @@ public partial class Plugins : MSGComponentBase
 
     protected override async Task OnInitializedAsync()
     {
-        this.ApplyFilters([], [ Event.PLUGINS_RELOADED, Event.CONFIGURATION_CHANGED, Event.HIGHLIGHT_DROP_ZONE, Event.PATHS_DROPPED ]);
-
-        // The whole page is the drop target, so users can drop a plugin archive anywhere on it:
-        this.dropZoneScope.TryBecomeDefaultZone(this);
+        this.ApplyFilters([], [ Event.PLUGINS_RELOADED, Event.CONFIGURATION_CHANGED ]);
 
         this.groupConfig = new TableGroupDefinition<IPluginMetadata>
         {
@@ -90,12 +79,6 @@ public partial class Plugins : MSGComponentBase
             await this.TryAutoAuditAssistantsAsync();
     }
 
-    protected override void DisposeResources()
-    {
-        this.dropZoneScope.ReleaseDefaultZone(this);
-        base.DisposeResources();
-    }
-
     #endregion
 
     private async Task PluginActivationStateChanged(IPluginMetadata pluginMeta)
@@ -275,7 +258,8 @@ public partial class Plugins : MSGComponentBase
     /// Highlights the plugin table while the user drags a file over the page, so it is visible
     /// where the file would land.
     /// </summary>
-    private string PluginTableClass => this.isDraggingOverPage
+    /// <param name="isDropTarget">Whether the page is the target of the drop being aimed right now.</param>
+    private static string PluginTableClass(bool isDropTarget) => isDropTarget
         ? "border-dashed border rounded-lg mud-border-primary border-4"
         : "border-dashed border rounded-lg";
 
@@ -570,54 +554,11 @@ public partial class Plugins : MSGComponentBase
             case Event.CONFIGURATION_CHANGED:
                 await this.InvokeAsync(this.StateHasChanged);
                 break;
-
-            case Event.HIGHLIGHT_DROP_ZONE when data is DropZoneHighlight highlight:
-                this.ApplyHighlight(this.IsThisZone(highlight.ZoneId));
-                break;
-
-            case Event.PATHS_DROPPED when data is DroppedPaths dropped:
-                // Whoever the drop was meant for, the drag is over and nothing stays highlighted:
-                this.ApplyHighlight(false);
-
-                if (!this.IsThisZone(dropped.ZoneId))
-                    return;
-
-                if (!this.CanCatchDroppedFile())
-                {
-                    LOG.LogDebug("The plugins page cannot import right now and swallowed {Count} dropped path(s).", dropped.Paths.Count);
-                    return;
-                }
-
-                await this.ImportDroppedPluginArchiveAsync(dropped.Paths);
-                break;
         }
     }
 
     #endregion
 
-    /// <summary>
-    /// Decides whether the named zone is this page.
-    /// </summary>
-    /// <param name="zoneId">The ID the hit test reported, or null when it hit nothing.</param>
-    private bool IsThisZone(string? zoneId) => zoneId is not null && zoneId == this.dropZoneScope.ScopeId;
-
-    /// <summary>
-    /// Marks the page as the drop target, or takes that mark away.
-    /// </summary>
-    /// <remarks>
-    /// The comparison is not for tidiness: a throttled drag-over event arrives about ten times per
-    /// second, and without it every one of them would render the whole plugin table anew.
-    /// </remarks>
-    private void ApplyHighlight(bool shouldBeHighlighted)
-    {
-        var highlighted = shouldBeHighlighted && this.CanCatchDroppedFile();
-        if (highlighted == this.isDraggingOverPage)
-            return;
-
-        this.isDraggingOverPage = highlighted;
-        this.StateHasChanged();
-    }
-
     /// <summary>
     /// Decides whether this page may process dropped files: only when the organization allows
     /// importing plugins at all and no import is running.