fix(strategy): report unknown --transform cleanly instead of KeyError traceback (Fixes #199)

[RealDiligent]

PR kind

• fix
• feat

Summary

Fixes #199 — python -m strategy --transform nope raised an uncaught KeyError traceback (exit 1) instead of the project CLI contract (error: … on stderr, exit 2).

• Validate the transform name via get_transform() before any GPU work in runner.run / runner.compare
• Catch KeyError alongside the existing (ValueError, RuntimeError, MemoryError) handler

Validation

• uv run --extra test python -m pytest tests/test_cli_errors.py -v (9 passed)
• uv run python -m strategy.smoke
• uv run --extra test python -m pytest tests/ strategy/tests/ eval/tests/ -q

GPU Result (required for feat PRs only)

N/A — fix lane.

Checklist

• CPU-safe validation passed
• My commits do not include Co-authored-by footers for coding agents
• Correctness gates pass

[zeokin]

Thanks — this fix is verified and I want to merge it, but it now conflicts with the just-merged #189 (fix/data-rank-reject). Both PRs append a new test function to tests/test_cli_errors.py at the same spot, so it's a trivial add/add conflict — your strategy/cli.py change merges cleanly on its own.

Please rebase onto the latest main and keep both test functions (yours for the unknown---transform error plus #189's for --data-rank). Once it's green again I'll merge. A new commit resets the bot's conflict timer.

[github-actions]

This PR currently has merge conflicts with the base branch. Please resolve them within 12 hours or the bot will close the PR automatically.