Show current guest OS version separately from base image version #2634

Is your feature request related to a problem? Please describe.

OrbStack labels the machine's creation image as Version, which looks like the
currently installed guest version.

For example, a machine created from nixos:25.11 and upgraded normally with
nixos-rebuild reports:

$ nixos-version
26.05.20260722.b3fe958

$ orbctl info nixpkgs-review-arm64
Distro: nixos
Version: 25.11

The JSON field is image.version, but the text and GUI do not clarify that it
means the original image.

Describe the solution you'd like

At minimum, rename the field to Base image version or Created from.
Ideally, show both values:

Created from: NixOS 25.11
Currently running: NixOS 26.05

Current guest detection could be best-effort and cached for stopped machines.
The existing image.version JSON field could remain for compatibility, with a
separate field for the detected guest version.

Describe alternatives you've considered

Running nixos-version manually, renaming the machine, or recreating it after
each upgrade. These workarounds are manual or discard useful machine state.

Additional context

Tested with OrbStack 2.2.2. Related issues #11 and #120 concern image selection
during creation, not distinguishing the original image from the current guest.