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.

[sparten11740]

utACK - some non-blocking comments

[sparten11740]

shouldn't this also be using setEnv to warn of conflicts in case the env var is already set?

[sparten11740]

not ideal in 3 (nit) aspects:

• fn name sounds like a predicate, not something you'd pass into map
• regex is constructed on each iteration
• options.quiet and ternary could be hoisted so that it doesn't need to be checked on every iteration:

 const identity = (value) => value
 const filterQuietOutput = options.quiet 
    ? (chunk) => chunk.split('\n').filter((line) => !outcomeRegex.test(line)).join('\n')
    : identity

[sparten11740]

I wonder if architecturally this could've been done in a more extensible way e.g. abstract this behind a reporter interface that receives the log output and internally decides whether to buffer, print right away, remove parts of the output, etc.