[Bug]: Sampler preview disappears when switching tabs or applications

Mirror of comfyanonymous/ComfyUI#8959 — moved to frontend repo since the fix is frontend-side.

## Description

When a sampler is running and showing a preview, switching to another browser tab or application causes the preview to disappear. When returning to the ComfyUI tab, the preview is gone even though the sampler is still running.

## Root Cause

This is a symptom of the broader Tab-Graph-Prompt State Sync issue (#3377). WebSocket messages (including preview data) are not properly associated with the originating workflow tab, causing state to be lost or misapplied when switching contexts.

## Original Issue

https://github.com/comfyanonymous/ComfyUI/issues/8959

┆Issue is synchronized with this [Notion page](https://www.notion.so/Issue-10688-Bug-Sampler-preview-disappears-when-switching-tabs-or-applications-3316d73d365081ae8385cca67e734c48) by [Unito](https://www.unito.io)