feat: add quiet test output mode

[exo-mv]

Summary

• add a --quiet flag that only reports failing test suites plus the final summary
• buffer node:test reporter output so passing suites stay hidden while failures keep useful diagnostics
• apply quiet filtering to pure/bundle subprocess output and handle watch-mode drain cycles

Verification

• npm run lint
• FORCE_COLOR=1 npm test
• focused quiet-mode smoke checks for passing suites, failing node:test suites, pure/bundle output, and watch mode

Note: plain npm test is color-sensitive in this shell because vendor matcher assertions expect colored output; FORCE_COLOR=1 npm test passes.