Milestone M3 — uv and uvw Scenario Coverage

Issue: #6 (https://github.com/joelvaneenwyk/py-launch-lab/issues/6)

Description

Extend the test matrix to cover all uv and uvw launch modes. This includes uv run, uvx, uv tool run, and uv tool install for both console and GUI fixture packages, producing per-scenario JSON evidence artifacts.

How it Works

1. Each uv/uvw invocation pattern is defined as a scenario in the matrix
2. The runner executes each scenario and records observable behaviour
3. Results are serialised to artifacts/json/ as per-scenario JSON files
4. Integration tests validate expected outcomes for each launch mode

Tasks

• [x] Run scenarios for uv run script.py, uv run script.pyw, uv run --gui-script
• [x] Run scenarios for uvx and uv tool run
• [x] Run uv tool install for console and GUI fixture packages
• [x] Integration tests: test_uv_run.py, test_uv_tool_install.py, test_uvx.py, test_uvw.py
• [x] Populate artifacts/json/ with per-scenario result JSON

Related Issues

• Depends on m2-python-vs-pythonw-launch.md - needs the process runner infrastructure

Next Steps

• [ ] Verify uv and uvw are available on the CI Windows runner
• [ ] Confirm fixture packages install cleanly via uv tool install
• [ ] Review JSON artifacts for completeness and schema compliance