Linux installer issues on Ubuntu 26.04: Vulkan step hard-fail and CMake generator typo (Nina)

Hi team, thanks for this project.

I tested the Linux flow on Ubuntu 26.04.1 LTS (kernel 7.0.0-31-generic) and found two blocking installer issues:

1) Vulkan step hard-fails if expected SDK artifact is not present/reachable
- Installer expects a specific Vulkan SDK installer file in /tmp path and aborts when missing.
- This blocks setup even when distro Vulkan packages are available.

2) CMake generator typo
- Build invocation uses `-G Nina`
- Fails with: `Could not create named generator Nina`
- Expected generator is `Ninja`

Environment:
- Ubuntu 26.04.1 LTS (resolute)
- Python 3.14.4
- Intel Core Ultra 9 185H

Expected:
- Installer should fallback gracefully when Vulkan SDK download/install path is unavailable.
- CMake generator should be valid (`Ninja`).

Actual:
- Setup aborts in Vulkan step and build fails at generator selection.

Workaround that succeeded:
- Manual venv + OpenVINO setup
- Install Intel NPU userspace from `intel/linux-npu-driver` release bundle
- Validate devices with OpenVINO (`CPU`, `GPU`, `NPU`)
- Run NPU inference successfully

Please consider:
- fixing `Nina` -> `Ninja`
- making Vulkan step resilient (fallback mode)
- documenting tested Ubuntu 26.04 package/source path explicitly

No file or test is named. Start by locating the installer entry points for the Vulkan setup and CMake build invocation, then reproduce the missing-SDK and `-G Nina` failures on Ubuntu. Done means the generator uses `Ninja` and an unavailable Vulkan SDK follows a documented fallback path without aborting setup.

Written by the indexing model from the issue text.