node:zlib: stream objects missing .on/.pipe/.write (Transform interface) + brotli fns + Z_* constants (43 radar runtime-fails)

[proggeramlug]

Summary

node:zlib is measurable now (#1778 linked the feature; compile-fail 50→3) and shows 43 runtime-fails. Clustered from the #800 radar (perry 0.5.1029):

Clusters (by impact)

1. zlib stream objects aren't proper streams (~15 tests) — Gzip/Deflate/Brotli* instances are missing the Transform-stream interface:
   • undefined.on (5), on is not a function (2) — e.g. test-zlib-close-after-error.js, test-zlib-object-write.js
   • undefined.pipe (4), pipe is not a function (2) — e.g. test-zlib-flush-drain-longblock.js
   • write is not a function (2) — e.g. test-zlib-brotli-flush.js
     So zlib.createGzip().pipe(...) / .on('data') / .write() don't work — the returned object isn't wired as a stream.
2. Unimplemented zlib functions (13 value is not a function) — brotli-heavy, e.g. test-zlib-brotli-16GB.js, test-zlib-brotli-from-brotli.js.
3. Z_ constants* — undefined.Z_OK (test-zlib-const.js).
4. Behavioral diffs (2), undefined.length (2).

Priority

The stream-interface gap (cluster 1) is the highest-leverage — it's the foundation most zlib usage builds on, and likely shares a root with the broader stream work. Brotli (cluster 2) is a distinct implementation gap.

Context: full --auto-optimize #800 sweep, perry 0.5.1029. zlib became measurable via #1778.