Test a C# worker

Test at three layers:

1. Pure .NET tests for vector kernels, state encoding, validation, and producer boundaries.
2. SQLLogicTest through a real DuckDB VGI extension for registration, SQL binding, Arrow IPC, lifecycle, optimizer, cancellation, and transport behavior.
3. Shared conformance and cross-language tests so C# agrees with canonical Python/Rust clients and with workers written in Python, Rust, Go, and TypeScript.

The upstream documentation project is executable:

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make docs_examples
make test_docs_examples

Its verifier builds Release, stages the SQL test with the absolute worker path, and invokes:

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uvx haybarn-unittest test/sql/examples.test

Use uvx haybarn-unittest; there is no reason to clone or build Haybarn for these checks. In CI, test the published executable and include at least one multi-batch case—single tiny batches miss many lifecycle and framing failures.