Importing Postman collection JSON ignores folder hierarchy and treats top-level folders as single API calls

### Expected Behavior

I expect to import the Postman JSON file and have all of my calls in their original nested sctructure.

For example, in Postman I have a collection called examples. There are folders in this collection, and underneath those folders are a number of calls:

I expect to see all of these calls when I import into Insomnia.

### Actual Behavior

Insomnia takes the call that is associated with the top-level folder (for example, `Examples (2025-10-08) > DB GET` and flattens it the folder so that all I get is the call associated with the top-level folder. I end up with this:

The DB GET folder cannot be expanded, or at least I cannot find any way to expand it. It is reduced to a single call instead of a folder of calls.

Unfortunately I cannot share the import file. It was simply exported from Postman to JSON (current version of Postman offers no options for export format).

### Reproduction Steps

_No response_

### Is there an existing issue for this?

- [x] I have searched the [issue tracker](https://www.github.com/Kong/insomnia/issues) for this problem.

### Which sync method do you use?

- [ ] Git sync.
- [ ] Insomnia Cloud sync.
- [ ] Local only

### Additional Information

_No response_

### Insomnia Version

12.3.0

### What operating system are you using?

Windows

### Operating System Version

Windows 11 Home

### Installation method

EXE file from website

### Last Known Working Insomnia version

n/a

Start by obtaining or creating a Postman-exported JSON collection with nested folders, then run the import flow in Insomnia on Windows. Compare the imported hierarchy with the source collection, including folders containing other folders and requests. Done means nested folders remain expandable and their requests are not represented as a single top-level API call.

Written by the indexing model from the issue text.