Make the default drop target follow the open panel

app/MindWork AI Studio/Assistants/DocumentAnalysis/DocumentAnalysisAssistant.razor

@@ -128,7 +128,9 @@ else
 
                 <MudTextField T="string" Disabled="@this.IsNoPolicySelectedOrProtected" @bind-Text="@this.policyAnalysisRules" Validation="@this.ValidateAnalysisRules" Immediate="@true" Label="@T("Analysis rules")" HelperText="@T("Please provide a description of your analysis rules. This rules will be used to instruct the AI on how to analyze the documents.")" Variant="Variant.Outlined" Margin="Margin.Normal" Lines="5" AutoGrow="@true" MaxLines="26" UserAttributes="@USER_INPUT_ATTRIBUTES" Class="mb-3"/>
 
-                <ReadFileContent Text="@T("Load analysis rules from document")" @bind-FileContent="@this.policyAnalysisRules" Disabled="@this.IsNoPolicySelectedOrProtected"/>
+                @* No default target for the rule zones: while the policy definition is open, three
+                   zones are in play, so each drop has to be aimed at the one it belongs to. *@
+                <ReadFileContent Text="@T("Load analysis rules from document")" @bind-FileContent="@this.policyAnalysisRules" EnableDragDrop="true" Disabled="@this.IsNoPolicySelectedOrProtected"/>
 
                 <MudJustifiedText Typo="Typo.body1" Class="mt-3">
                     @T("After the AI has processed all documents, it needs your instructions on how the result should be formatted. Would you like a structured list with keywords or a continuous text? Should the output include emojis or be written in formal business language? You can specify all these preferences in the output rules. There, you can also predefine a desired structure—for example, by using Markdown formatting to define headings, paragraphs, or bullet points.")
@@ -136,7 +138,7 @@ else
 
                 <MudTextField T="string" Disabled="@this.IsNoPolicySelectedOrProtected" @bind-Text="@this.policyOutputRules" Validation="@this.ValidateOutputRules" Immediate="@true" Label="@T("Output rules")" HelperText="@T("Please provide a description of your output rules. This rules will be used to instruct the AI on how to format the output of the analysis.")" Variant="Variant.Outlined" Margin="Margin.Normal" Lines="5" AutoGrow="@true" MaxLines="26" UserAttributes="@USER_INPUT_ATTRIBUTES" Class="mb-3"/>
 
-                <ReadFileContent Text="@T("Load output rules from document")" @bind-FileContent="@this.policyOutputRules" Disabled="@this.IsNoPolicySelectedOrProtected"/>
+                <ReadFileContent Text="@T("Load output rules from document")" @bind-FileContent="@this.policyOutputRules" EnableDragDrop="true" Disabled="@this.IsNoPolicySelectedOrProtected"/>
 
                 @if (this.SettingsManager.ConfigurationData.App.ShowAdminSettings)
                 {
@@ -153,7 +155,7 @@ else
 
         <MudDivider Style="height: 0.25ch; margin: 1rem 0;" Class="mt-6" />
 
-        <ExpansionPanel HeaderIcon="@Icons.Material.Filled.DocumentScanner" HeaderText="@(T("Document selection - Policy") + $": {this.selectedPolicy?.PolicyName}")" IsExpanded="@(this.selectedPolicy?.IsProtected ?? false)">
+        <ExpansionPanel HeaderIcon="@Icons.Material.Filled.DocumentScanner" HeaderText="@(T("Document selection - Policy") + $": {this.selectedPolicy?.PolicyName}")" IsExpanded="@this.documentSelectionExpanded" ExpandedChanged="@this.DocumentSelectionExpandedChanged">
             <MudText Typo="Typo.h5" Class="mb-1">
                 @T("Policy Description")
             </MudText>
@@ -166,7 +168,10 @@ else
                 @T("Documents for the analysis")
             </MudText>
 
-            <AttachDocuments Name="Document Analysis Files" @bind-DocumentPaths="@this.loadedDocumentPaths" CatchAllDocuments="true" UseSmallForm="false" Provider="@this.ProviderSettings"/>
+            @* The whole assistant catches drops, but only while this panel is the open one. A
+               collapsed panel keeps its content in the DOM with a height of zero, so without this
+               the invisible zone would swallow the drops meant for the policy definition. *@
+            <AttachDocuments Name="Document Analysis Files" @bind-DocumentPaths="@this.loadedDocumentPaths" CatchAllDocuments="@this.documentSelectionExpanded" UseSmallForm="false" Provider="@this.ProviderSettings"/>
 
         </ExpansionPanel>
     </MudExpansionPanels>

app/MindWork AI Studio/Assistants/DocumentAnalysis/DocumentAnalysisAssistant.razor.cs

@@ -244,6 +244,7 @@ public partial class DocumentAnalysisAssistant : AssistantBaseCore<NoSettingsPan
         }
 
         this.policyDefinitionExpanded = !this.selectedPolicy?.IsProtected ?? true;
+        this.documentSelectionExpanded = !this.policyDefinitionExpanded;
         await base.OnInitializedAsync();
         this.ApplyFilters([], [ Event.CONFIGURATION_CHANGED, Event.PLUGINS_RELOADED ]);
         this.UpdateProviders();
@@ -285,6 +286,17 @@ public partial class DocumentAnalysisAssistant : AssistantBaseCore<NoSettingsPan
     private bool policyIsProtected;
     private bool policyHidePolicyDefinition;
     private bool policyDefinitionExpanded;
+
+    /// <summary>
+    /// Whether the document selection panel is the open one.
+    /// </summary>
+    /// <remarks>
+    /// Only one of the two panels is ever open, so this is normally the opposite of the field above
+    /// -- but not always: the user can collapse both. It is tracked rather than derived because it
+    /// decides whether the document zone is the default target of the whole assistant, and a
+    /// collapsed zone must not hold that role.
+    /// </remarks>
+    private bool documentSelectionExpanded;
     private string policyName = string.Empty;
     private string policyDescription = string.Empty;
     private string policyAnalysisRules = string.Empty;
@@ -333,7 +345,11 @@ public partial class DocumentAnalysisAssistant : AssistantBaseCore<NoSettingsPan
         state.Restore(SELECTED_POLICY_STATE_KEY, value => this.selectedPolicy = value);
         state.Restore(POLICY_IS_PROTECTED_STATE_KEY, value => this.policyIsProtected = value);
         state.Restore(POLICY_HIDE_POLICY_DEFINITION_STATE_KEY, value => this.policyHidePolicyDefinition = value);
-        state.Restore(POLICY_DEFINITION_EXPANDED_STATE_KEY, value => this.policyDefinitionExpanded = value);
+        state.Restore(POLICY_DEFINITION_EXPANDED_STATE_KEY, value =>
+        {
+            this.policyDefinitionExpanded = value;
+            this.documentSelectionExpanded = !value;
+        });
         state.Restore(POLICY_NAME_STATE_KEY, value => this.policyName = value);
         state.Restore(POLICY_DESCRIPTION_STATE_KEY, value => this.policyDescription = value);
         state.Restore(POLICY_ANALYSIS_RULES_STATE_KEY, value => this.policyAnalysisRules = value);
@@ -359,6 +375,7 @@ public partial class DocumentAnalysisAssistant : AssistantBaseCore<NoSettingsPan
         this.selectedPolicy = policy;
         this.ResetForm();
         this.policyDefinitionExpanded = !this.selectedPolicy?.IsProtected ?? true;
+        this.documentSelectionExpanded = !this.policyDefinitionExpanded;
         this.ApplyPolicyPreselection(preferPolicyPreselection: true);
         
         this.Form?.ResetValidation();
@@ -368,6 +385,22 @@ public partial class DocumentAnalysisAssistant : AssistantBaseCore<NoSettingsPan
     private Task PolicyDefinitionExpandedChanged(bool isExpanded)
     {
         this.policyDefinitionExpanded = isExpanded;
+
+        // The panels do not allow multi expansion, so opening this one closes the other:
+        if (isExpanded)
+            this.documentSelectionExpanded = false;
+
+        return Task.CompletedTask;
+    }
+
+    private Task DocumentSelectionExpandedChanged(bool isExpanded)
+    {
+        this.documentSelectionExpanded = isExpanded;
+
+        // The panels do not allow multi expansion, so opening this one closes the other:
+        if (isExpanded)
+            this.policyDefinitionExpanded = false;
+
         return Task.CompletedTask;
     }
     
@@ -457,6 +490,7 @@ public partial class DocumentAnalysisAssistant : AssistantBaseCore<NoSettingsPan
         this.policyIsProtected = state;
         this.selectedPolicy.IsProtected = state;
         this.policyDefinitionExpanded = !state;
+        this.documentSelectionExpanded = state;
         await this.AutoSave(true);
     }
 
@@ -634,6 +668,7 @@ public partial class DocumentAnalysisAssistant : AssistantBaseCore<NoSettingsPan
 
         // Update the expansion state based on the policy protection:
         this.policyDefinitionExpanded = !this.selectedPolicy?.IsProtected ?? true;
+        this.documentSelectionExpanded = !this.policyDefinitionExpanded;
 
         // Update available providers:
         this.UpdateProviders();