Pre-scaffolding for the next batch (CVE-2023-32233, CVE-2023-4622,
CVE-2022-25636, CVE-2023-0179). Each module ships as a 21-line
stub returning PRECOND_FAIL; parallel agents fill in the real
detect/exploit/--full-chain implementations.
This commit keeps registry.h / iamroot.c / Makefile in one place
so the 4 parallel agents don't collide on shared-file edits — they
each own a single iamroot_modules.c.
Build clean on Debian 6.12.86; --list shows all 24 modules
including the 4 new stubs.
