The previous err_maxval hardcoded the list of AKERR_* codes, which silently
rots the moment a code is added. Instead, parse the generated akerror.h at
runtime: discover every "#define AKERR_<NAME> (AKERR_LAST_ERRNO_VALUE + N)",
take the highest offset actually defined, and assert AKERR_MAX_ERR_VALUE covers
it. A compile-time cross-check ties the parsed ceiling to the compiled macro so
the test can't pass by reading a stale header.
CMake injects the header path as AKERR_GENERATED_HEADER. Verified: the test
fails (max_err_value >= highest_code) when pointed at a +15 header while
AKERR_BADEXC is +17, and now also strengthens header mutation coverage.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Andrew Kesterson
536a269aad
