Port Bun only-failures reporter matrix

Track the next focused Bun compatibility tranche from #66.

Scope:

• run the byte-identical upstream js/bun/test/only-failures.test.ts corpus under Home
• match --only-failures output and code frames while retaining aggregate pass/skip/todo/fail counts
• suppress (pass) reporter lines for single-file, multi-file, and bunfig-driven runs
• derive the detailed reporter fixture from the upstream inline snapshot
• add permanent Home regression coverage and run the full home_test gate

This issue will be closed by the direct-main implementation commit.

Completed in 2957a3f (feat(test): port only failures reporter). The byte-identical upstream only-failures.test.ts now passes all three modes under Home: direct --only-failures, multi-file, and bunfig configuration. Detailed code frames and aggregate counts come from the upstream inline snapshot, while (pass) reporter lines stay suppressed. Permanent aggregate coverage was added. Validation passed: exact corpus 3/3, focused regression, both upstream byte comparisons, formatter/diff checks, and full home_test (1089 tests, 1 expected skip, 0 failures).