Port from Kilo-Org/kilocode#12698: report signal-terminated commands with
a human-readable note instead of a bare numeric exit code.
Kilo's fix settles a signal-killed process as the conventional 128+signum
exit code so its bash tool stops hanging. Hermes already produces numeric
codes for signal deaths (subprocess -signum, or the shell's 128+signum),
but the model saw a bare exit_code=-9 or 137 and burned turns
mis-diagnosing (137 = OOM kill being the most common). This adapts the
idea to Hermes' existing exit-code semantics tier:
- _interpret_signal_exit(): maps negative codes (definite signal death)
and the 128+signum band (hedged with 'usually') to a note naming the
signal and its likely cause, wired into _interpret_exit_code() ahead of
the per-command semantics table.
- Curated signal table (SIGKILL/SIGSEGV/SIGTERM/SIGABRT/...) so ambiguous
application exit codes are never mislabeled; uncurated 128+N codes stay
silent, SIGINT is excluded (executor's interrupt-marker path owns
rc=130).
- Notes surface via the existing exit_code_meaning result field.
E2E verified against real SIGSEGV/SIGKILL processes.
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