File in context indication (#4990)

# Description of Changes

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Please provide a summary of the changes, including:

- What was changed
- Why the change was made
- Any challenges encountered

Closes #(issue_number)
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## Checklist

### General

- [ ] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [ ] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md)
(if applicable)
- [ ] I have read the [How to add new languages to
Stirling-PDF](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md)
(if applicable)
- [ ] I have performed a self-review of my own code
- [ ] My changes generate no new warnings

### Documentation

- [ ] I have updated relevant docs on [Stirling-PDF's doc
repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/)
(if functionality has heavily changed)
- [ ] I have read the section [Add New Translation
Tags](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)

### Translations (if applicable)

- [ ] I ran
[`scripts/counter_translation.py`](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/docs/counter_translation.md)

### UI Changes (if applicable)

- [ ] Screenshots or videos demonstrating the UI changes are attached
(e.g., as comments or direct attachments in the PR)

### Testing (if applicable)

- [ ] I have tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md#6-testing)
for more details.

frontend/src/core/contexts/FileManagerContext.tsx

@@ -20,6 +20,7 @@ interface FileManagerContextValue {
   fileGroups: Map<FileId, StirlingFileStub[]>;
   loadedHistoryFiles: Map<FileId, StirlingFileStub[]>;
   isLoading: boolean;
+  activeFileIds: FileId[];
 
   // Handlers
   onSourceChange: (source: 'recent' | 'local' | 'drive') => void;
@@ -63,6 +64,7 @@ interface FileManagerProviderProps {
   modalHeight: string;
   refreshRecentFiles: () => Promise<void>;
   isLoading: boolean;
+  activeFileIds: FileId[];
 }
 
 export const FileManagerProvider: React.FC<FileManagerProviderProps> = ({
@@ -77,6 +79,7 @@ export const FileManagerProvider: React.FC<FileManagerProviderProps> = ({
   modalHeight,
   refreshRecentFiles,
   isLoading,
+  activeFileIds,
 }) => {
   const [activeSource, setActiveSource] = useState<'recent' | 'local' | 'drive'>('recent');
   const [selectedFileIds, setSelectedFileIds] = useState<FileId[]>([]);
@@ -618,6 +621,7 @@ export const FileManagerProvider: React.FC<FileManagerProviderProps> = ({
     fileGroups,
     loadedHistoryFiles,
     isLoading,
+    activeFileIds,
 
     // Handlers
     onSourceChange: handleSourceChange,
@@ -654,6 +658,7 @@ export const FileManagerProvider: React.FC<FileManagerProviderProps> = ({
     fileGroups,
     loadedHistoryFiles,
     isLoading,
+    activeFileIds,
     handleSourceChange,
     handleLocalFileClick,
     handleFileSelect,