Bug Description

When installing OpenViking from source (e.g. on Python 3.14 where no pre-built wheel is available), setup.py silently skips the Rust CLI build when cargo is not installed, then crashes at the artifact check with an unhelpful RuntimeError.

Steps to Reproduce

1. Use python 3.14
2. Ensure Rust/cargo is NOT installed
3. Run: pip install openviking --upgrade --force-reinstall

Expected Behavior

Build should either fail early with a clear message like "Rust toolchain (cargo) is required to build the ov CLI. Install it from https://rustup.rs", or the artifact check should be skipped if the component is truly optional.

Actual Behavior

Build silently skips the Rust CLI compilation (prints a warning), then crashes at the artifact check with: RuntimeError: ov CLI build did not produce required ov at /path/to/openviking/bin/ov

Error Logs:
RuntimeError: ov CLI build did not produce required ov at /Users/user/.cache/uv/sdists-v9/pypi/openviking/0.2.6/.../src/openviking/bin/ov

hint: This usually indicates a problem with the package or the build environment.

Minimal Reproducible Example

Error Logs

OpenViking Version

0.2.6

Python Version

3.14.2

Operating System

macOS

Model Backend

None

Additional Context

No response