Feature/v2/viewer tabs (#4646)

# 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)

### 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.

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: James Brunton <james@stirlingpdf.com>
Co-authored-by: Claude <noreply@anthropic.com>

frontend/src/components/fileEditor/FileEditorThumbnail.tsx

@@ -45,6 +45,7 @@ const FileEditorThumbnail = ({
   selectedFiles,
   onToggleFile,
   onCloseFile,
+  onViewFile,
   _onSetStatus,
   onReorderFiles,
   onDownloadFile,
@@ -205,6 +206,11 @@ const FileEditorThumbnail = ({
     onToggleFile(file.id);
   };
 
+  const handleCardDoubleClick = () => {
+    if (!isSupported) return;
+    onViewFile(file.id);
+  };
+
   // ---- Style helpers ----
   const getHeaderClassName = () => {
     if (hasError) return styles.headerError;
@@ -226,6 +232,7 @@ const FileEditorThumbnail = ({
       role="listitem"
       aria-selected={isSelected}
       onClick={handleCardClick}
+      onDoubleClick={handleCardDoubleClick}
     >
       {/* Header bar */}
       <div