Native mounts do not work on Windows 11 with Hyper-V

**To Reproduce**
Create some folder on disk, make sure your account is not explicitly listed - just be part of one of the allowed accounts that have full access privilege, then try to mount it into a VM using Powershell terminal with commands such as
```Powershell
multipass mount -t native "D:\Code" kub-control-01`:/home/ubuntu/test
```

Getting error:
```
mount failed: The following errors occurred:
error mounting "/home/ubuntu/test": cannot access "D:\Code"
```

Now add your account to the list of allowed users explicitly, make sure you have full access privilege checkbox checked in the Windows Explorer folder permissions dialog.

Now it will ask for password, then error:
```
Please enter your user password to allow Windows mounts:

mount failed: The following errors occurred:
error mounting "/home/ubuntu/test": Error: mount error: could not resolve address for desktop: Unknown error
```

Attached the events.

**Expected behavior**
What did you expect to happen?

I want Multipass to be able to mount folders into the VM, as documented.

**Logs**
In the Event Log before adding myself to allowed users explicitly,
I can see Multipass issues Powershell command `(Get-Acl 'D:\Code').Access | ?{($_.IdentityReference -match 'roman') -and ($_.FileSystemRights -eq 'FullControl')}`

I am the administrator, but my login name is not explicitly listed in the ACL, instead the access is via group. I am also the owner of that folder.

So it seems like the command does not return my login, and Multipass believes I don't have access to that folder.

Then after I add myself explicitly, there's a bunch of events related to smb share, which I attached here.

**Additional info**
- OS: Windows 11 Pro 24H2, OS Build 26100.4351
- CPU architecture or model: 64bit, Intel Core i9-13900K
- multipass 1.15.1+win, multipassd 1.15.1+win
- ```
Name: kub-control-01
State: Running
Snapshots: 0
IPv4: 172.27.94.147
Release: Ubuntu 24.10
Image hash: 8446856f1903 (Ubuntu 24.10)
CPU(s): 4
Load: 0.00 0.03 0.02
Disk usage: 1.9GiB out of 9.6GiB
Memory usage: 346.1MiB out of 2.8GiB
Mounts: --

Name: kub-control-lb
State: Running
Snapshots: 0
IPv4: 172.27.91.27
Release: Ubuntu 24.10
Image hash: 8446856f1903 (Ubuntu 24.10)
CPU(s): 2
Load: 0.00 0.00 0.00
Disk usage: 1.9GiB out of 4.8GiB
Memory usage: 184.4MiB out of 380.0MiB
Mounts: --
```
- ```
multipass get local.driver
hyperv
```

**Additional context**
Looks like two piles of issues here,
- the logic to verify file access is not documented, and doesn't look correct either
- problems with mounting the folder

Reproduce the native mount failures from the PowerShell commands in the report on Windows 11 with the Hyper-V driver, checking the Event Log and ACL output before and after explicitly granting access. Trace the native mount and Windows file-access checks, then verify that an allowed folder mounts successfully without requiring an explicit user ACL entry.

Written by the indexing model from the issue text.