fix(visualization): revert filePanelFileSelector track expression change

The track-by-fileName change caused an e2e test failure in
uploadFilesButton because mat-select value binding relies on object
identity. Reverting to original track-by-identity.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: 2 people

visualization/app/codeCharta/ui/filePanel/filePanelFileSelector/filePanelFileSelector.component.html

@@ -12,7 +12,7 @@
         <button class="cc-file-select-action-button" (click)="handleSelectZeroFiles()">None</button>
         <button class="cc-file-select-action-button" (click)="handleInvertSelectedFiles()">Invert</button>
     </div>
-    @for (file of filesInUI; track file.file.fileMeta.fileName) {
+    @for (file of filesInUI; track file) {
         <mat-option class="cc-file-name" [value]="file.file" [ngStyle]="{ 'text-decoration': file.isRemoved ? 'line-through' : 'none' }">
             {{ file.file.fileMeta.fileName | removeExtension }}
             <cc-remove-file-button