Re-opening an already opened workflow file overwrites all current settings

### Prerequisites

- [x] I am running the latest version of ComfyUI
- [x] I have searched existing issues to make sure this isn't a duplicate
- [x] I have tested with all custom nodes disabled ([see how](https://docs.comfy.org/troubleshooting/custom-node-issues#step-1%3A-test-with-all-custom-nodes-disabled))

### What happened?

If you have a workflow opened and then re-open that same workflow file on disk, the expected and desired behavior would be to open a new tab for a NEW workflow, regardless if you already have that file opened in a tab. This way, you can work on the same workflow with different options. But instead, ComfyUI just blindly overwrites your existing workflow costing you hours of work. Even if you saved your options, it just deletes everything.

### Steps to Reproduce

1. Open a workflow from disk
2. Make numerous edits or do some runs of that workflow
3. Go to File->Open and re-open that same workflow.
4. It overwrites and deletes all the work you previously did, even if you "saved" it. Not entirely sure what save means in comfy tbh.

### How is this affecting you?

Crashes ComfyUI completely

### ComfyUI Frontend Version

1.28.7

### Browser

Chrome/Chromium

### Console Errors

```javascript

```

### Logs

```shell

```

### Additional Context

Extremely frustrating behavior.

┆Issue is synchronized with this [Notion page](https://www.notion.so/Issue-6309-Re-opening-an-already-opened-workflow-file-overwrites-all-current-settings-2986d73d365081219280f7dfe63208c1) by [Unito](https://www.unito.io)