[Bug]: Opening a saved workflow while another workflow is open overwrites the initial workflow with the second

### Frontend Version

1.18.10

### Expected Behavior

User should be able to open workflows while another is open without overwriting any other workflows.

### Actual Behavior

When the user opens a workflow with another already open, the one that is already open gets overwritten and replaced with the second one, potentially causing a user to lose work.

### Steps to Reproduce

1. Run comfyui with all external nodes disabled
2. Create a workflow and add a Clip Text Encode (Prompt) node.
3. Save workflow as BugA.
4. Create another workflow with 2 Clip Text Encode (Prompt) nodes.
5. Save workflow as BugB.
6. Exit BugB and keep BugA open.
7. Open BugB in a new tab
8. Check BugA
9. See if BugA has 2 nodes
10. If it doesn't, close BugA and reopen it
11. Check BugB and see if it has 1 node.
12. If it doesn't, close BugB and repeat the process.

It may take a couple cycles (as few a 1 but it's taken up to 9 for me ) but by cycling through the workflows, it'll eventually replace the already opened workflow contents with the contents of the opened workflow. If the user saves it, then they lose the original workflow.

### Debug Logs

```powershell
Checkpoint files will always be loaded safely.
Total VRAM 24564 MB, total RAM 65293 MB
pytorch version: 2.6.0+cu126
Set vram state to: NORMAL_VRAM
Device: cuda:0 NVIDIA GeForce RTX 3090 Ti : cudaMallocAsync
Using pytorch attention
Python version: 3.10.11 (tags/v3.10.11:7d4cc5a, Apr 5 2023, 00:38:17) [MSC v.1929 64 bit (AMD64)]
ComfyUI version: 0.3.33
ComfyUI frontend version: 1.18.10
[Prompt Server] web root: H:\Python\lib\site-packages\comfyui_frontend_package\static

Import times for custom nodes:
0.0 seconds: G:\GIT\ComfyUI\custom_nodes\websocket_image_save.py

Starting server

To see the GUI go to: http://127.0.0.1:8188
```

### Browser Logs

api.ts:256 Running on 127.0.0.1:8188
App.vue:45 ComfyUI Front-end version: 1.18.10
:8188/api/userdata/comfy.templates.json:1


Failed to load resource: the server responded with a status of 404 (Not Found)

### Setting JSON

That file doesn't exist on my system

### What browsers do you use to access the UI ?

Google Chrome

### Other Information

https://github.com/user-attachments/assets/a7a0156a-5bf7-4a88-af92-d5b22cf4fd19

┆Issue is synchronized with this [Notion page](https://www.notion.so/Issue-3865-Bug-Opening-a-saved-workflow-while-another-workflow-is-open-overwrites-the-initial--1f16d73d365081bf8abdfcbf6ea32660) by [Unito](https://www.unito.io)