Measured failure taxonomy for Vercel/Conductor sandboxes (missing /dev/fd,
64M /dev/shm, seccomp-supervisor access(2) EACCES under load, uid-1000
processes with FULL capabilities defeating chmod-denial tests, no X server,
no git identity, Conductor git-shim exit-code laundering) plus the
idempotent script that treats all of it and seeds the run recipe.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>