`sqlmesh test` should treat model file paths as test selectors

[cmgoffena13]

Summary

sqlmesh test already takes multiple positional args, but they are test YAML paths only. Passing a model file looks that path up in the test-file index, matches nothing, and exits 0. A pre-commit hook that passes staged model files would silently run no tests.

--select-model takes names, not paths. tests= and model_names= are unioned, so you cannot pass a model file and a test YAML together and get both.

Current behavior

• sqlmesh test tests/test_a.yaml runs that file
• sqlmesh test models/a.sql runs zero tests and succeeds
• sqlmesh test tests/test_b.yaml --select-model a runs only tests that are in that file and target model a

Proposed CLI

sqlmesh test --local models/a.sql tests/test_b.yaml

Each positional arg is either:

• a test YAML (or file.yaml::test_name) → those tests, or
• a model file → unit tests for that model.

The two sets are a union. Staging models/a.sql and tests/test_b.yaml runs a’s tests and everything in b’s file.

Acceptance

• Model .sql / .py paths select that model’s tests even if the YAML path did not change
• Test YAML paths still work
• Mixed args are unioned, not intersected
• A path that is neither a known model file nor a known test file errors (no silent pass)
• --select-model name selectors keep current behavior