On Debian, /etc/os-release defines VERSION="13 (trixie)". runner-install
sourced it into the main shell for the Debian-family guard, overwriting the
script's empty $VERSION: the latest-release resolution was skipped and the
download URL became .../v13 (trixie)/... -> curl (3) malformed URL. A
--version pin was clobbered the same way (guards run after arg parsing).
Read ID/ID_LIKE via a subshell in both runner-install and bootstrap (same
pattern, no collision there yet), and add a harness guard that fails on any
future main-shell sourcing of os-release.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
