Limit a page to one drop zone per layer

app/MindWork AI Studio/Assistants/BatchProcessing/AssistantBatchProcessing.razor

@@ -7,9 +7,7 @@
     @T("Input")
 </MudText>
 
-@* This page carries a second drop zone for the instructions, so neither of them catches all
+<SelectDirectory Label="@T("Folder containing your documents")" DirectoryDialogTitle="@T("Select the folder containing your documents")" @bind-Directory="@this.inputDirectory" Validation="@this.ValidateInputDirectory" Disabled="@this.isProcessingBatch"/>
-   documents: with two targets, only the one under the mouse may take the drop. *@
-<SelectDirectory Label="@T("Folder containing your documents")" DirectoryDialogTitle="@T("Select the folder containing your documents")" @bind-Directory="@this.inputDirectory" Validation="@this.ValidateInputDirectory" Disabled="@this.isProcessingBatch" EnableDragDrop="true" Layer="@DropLayers.ASSISTANTS"/>
 
 <MudStack Row="true" AlignItems="AlignItems.Center" Spacing="2" Class="mb-1">
     <MudTextField T="string" @bind-Text="@this.filePatterns" Validation="@this.ValidateFilePatterns" Immediate="@true" Disabled="@this.isProcessingBatch" Label="@T("File patterns")" HelperText="@T("Which files should be processed? Separate multiple patterns with a semicolon, e.g., *.pdf;*.docx")" AdornmentIcon="@Icons.Material.Filled.FilterAlt" Adornment="Adornment.Start" Variant="Variant.Outlined" Margin="Margin.Normal" Class="flex-grow-1" UserAttributes="@USER_INPUT_ATTRIBUTES"/>
@@ -46,7 +44,7 @@
 
 @if (this.promptSource is BatchProcessingPromptSource.FREE_PROMPT)
 {
-    <ReadFileContent Text="@T("Load prompt from file")" @bind-FileContent="@this.freePrompt" EnableDragDrop="true" Layer="@DropLayers.ASSISTANTS" Disabled="@this.isProcessingBatch"/>
+    <ReadFileContent Text="@T("Load prompt from file")" @bind-FileContent="@this.freePrompt" EnableDragDrop="true" Layer="@DropLayers.ASSISTANTS" CatchAllDocuments="true" Disabled="@this.isProcessingBatch"/>
 
     <MudTextField T="string" @bind-Text="@this.freePrompt" Validation="@this.ValidateFreePrompt" Immediate="@true" Disabled="@this.isProcessingBatch" Label="@T("What should the AI do with each document?")" HelperText="@T("These instructions are applied to every single document of the batch run.")" Variant="Variant.Outlined" Margin="Margin.Normal" Lines="5" AutoGrow="@true" MaxLines="26" Class="mb-3" UserAttributes="@USER_INPUT_ATTRIBUTES"/>
 
@@ -54,7 +52,7 @@
 }
 else if (this.promptSource is BatchProcessingPromptSource.FILE_IMPORT)
 {
-    <ReadFileContent Text="@T("Select the file with your instructions")" @bind-FileContent="@this.ImportedPrompt" Filter="@([FileTypes.MARKDOWN])" ShowAttachedDocumentState="@true" EnableDragDrop="true" Layer="@DropLayers.ASSISTANTS" Disabled="@this.isProcessingBatch"/>
+    <ReadFileContent Text="@T("Select the file with your instructions")" @bind-FileContent="@this.ImportedPrompt" Filter="@([FileTypes.MARKDOWN])" ShowAttachedDocumentState="@true" EnableDragDrop="true" Layer="@DropLayers.ASSISTANTS" CatchAllDocuments="true" Disabled="@this.isProcessingBatch"/>
 
     @if (!string.IsNullOrWhiteSpace(this.promptFilePath))
     {

app/MindWork AI Studio/Components/PathDropZone.razor.cs

@@ -36,6 +36,15 @@ public partial class PathDropZone : MSGComponentBase
     /// <summary>
     /// Catch all documents that are hovered over the AI Studio window and not only over the drop zone.
     /// </summary>
+    /// <remarks>
+    /// Practically every zone needs this today. Hovering is detected through mouse events, and no
+    /// webview delivers those while a native drag is in progress, so a zone without this flag
+    /// hardly ever catches anything. The consequence is that two zones of the same layer cannot be
+    /// told apart: the one carrying this flag takes every drop, including the ones meant for the
+    /// other. A page may therefore hold only one zone per layer. Lifting that limit needs the
+    /// cursor position, which the runtime receives from Tauri and currently discards in
+    /// app_window.rs.
+    /// </remarks>
     [Parameter]
     public bool CatchAllDocuments { get; set; }
 
@@ -149,8 +158,9 @@ public partial class PathDropZone : MSGComponentBase
         if(this.Disabled || this.numDropAreasAboveThis > 0)
             return;
 
-        // The webview gets no DOM drag events while a native drag is in progress, so the mouse is
+        // A native drag delivers no DOM events at all, mouse events included. This fires before a
-        // what tells us whether the user is aiming at this zone:
+        // drag begins, while the pointer still moves freely, which makes it a hint about where the
+        // user is aiming rather than a reliable signal. See the remarks on CatchAllDocuments:
         this.isComponentHovered = true;
         this.SetDragClass();
         this.StateHasChanged();