The test job ran the entire suite on 3 OSes x 3 Node lines x 4 package
managers, 33 full runs per push. Windows lanes took 28 to 39 minutes and
macOS 14 to 19, so one push queued about 1.5 hours of wall clock behind
runner concurrency, and timing-sensitive tests got 33 chances to flake.
The package-manager axis only ever changed one environment variable that
nine suites read.
Now there are 13 lanes. Five run the full suite: Linux on Node 18, 20
and 22, plus Windows and macOS on Node 22. Eight are package-manager
lanes on Node 22 that run only the suites which read
CLAUDE_CODE_PACKAGE_MANAGER or CLAUDE_PACKAGE_MANAGER; the file list is
grepped at run time so it cannot drift as tests are added. Full lanes
use the runner's 4-process pool on Linux and macOS; Windows stays serial
because its process spawn and temp-dir cleanup are the flaky part.
