AKERR_MAX_ERR_VALUE was AKERR_LAST_ERRNO_VALUE + 15, but the highest defined
code, AKERR_BADEXC, is + 17 (AKERR_NOT_IMPLEMENTED is + 16). akerr_name_for_status
rejects any status above the max, so those codes could never have a registered
name and the AKERR_BADEXC registration in akerr_init was dead code -- a gap
found by mutation testing. Bump the max to + 17.
- err_maxval: new test asserting the reserved AKERR_* range exceeds the number
of AKERR_* codes and that every code is individually indexable. Fails against
the old + 15 value (verified), guarding against regression.
- err_error_names: now also checks AKERR_BADEXC's name, which the fix makes
reachable.
Mutation score on src/error.c rises 71% -> 74%: the previously-dead BADEXC
registration and the name_for_status upper-bound check are now killable.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
