fix(npm): use 128+signal exit code in mycelium.cjs launcher for SIGTERM/SIGINT

[aimasteracc]

Summary

Fixed in PR #535 (merged to develop, squash 3f812410, 2026-06-04T13:07Z).

signalToExitCode() now returns 128 + signal_number for all common POSIX signals including crash signals:

• SIGINT → 130, SIGTERM → 143, SIGHUP → 129
• SIGABRT → 134, SIGSEGV → 139, SIGILL → 132, SIGBUS → 135, SIGFPE → 136, SIGTRAP → 133

TDD: RED→GREEN confirmed (9/9 node --test). Will ship in v0.2.1.

Signed-off-by: aimasteracc yuaishengtrader@gmail.com