#675 test: add converter tests

Summary by cubic

Adds integration tests for the converter pipeline, covering every format target per converter and golden byte comparisons for sample conversions. The all-formats test asserts each declared target either produces a non-empty file or is listed in expected-failures.json, and the golden tests compare output byte-for-byte against checked-in reference files. No production code changes.

• Mutes converter stdout/stderr during the all-formats run and pins the expected target and success counts.
• Ignores the checked-in outputs directory in ESLint, Prettier, and knip configs so generated binary files stay out of linting.
• Moves the integration-test path ignore from the test script into bunfig.toml.