Root cause found via gdb backtrace on the runner (thread::pool_init crashed from main -> testing runner): the CI container sets `ulimit -s unlimited`, so getrlimit(RLIMIT_STACK) returns RLIM_INFINITY. core:thread passes that to pthread_attr_setstacksize, pthread_create fails, and thread.create() returns nil, which core:testing's pool_init dereferences without a nil check. Reproduced and confirmed fixed in an ubuntu:24.04 container with the same Odin build. `just test` now clamps the stack limit before running odin test. Also removes the gdb diagnostic step added to debug this. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>