runners: support deno test

[OllieinCanada]

Closes #3

Summary

Add focused support for deno test as one of the test runners requested in #3.

• recognize direct and wrapped invocations such as deno test and npx deno test
• parse Deno's final ok | N passed | N failed / FAILED | ... summary
• remain Unknown when the final summary is absent or reports zero tests
• retain the exact summary line as evidence

Validation

The fixtures are based on output captured from real Deno 2.9.5 passing and failing runs. Regression tests cover pass, failure, wrapped invocation, zero-test, and incomplete-output cases.

• cargo test deno_test -- --nocapture — 2 passed
• cargo fmt --all --check — passed
• cargo clippy --all-targets --all-features -- -D warnings — passed
• cargo test --all-features — 106 unit tests and 1 integration test passed
• git diff --check — passed