Architectural cleanup: the uid translation is a build-time concern
(the sandbox produces sandbox-uid files); having the gameserver path
unwind that producer-side decision on every mount means the mount
helper carries idmap lifecycle code it shouldn't need. Moving the
idmap into the script-sandbox bind makes files land left4me-owned on
disk, drops ~140 lines from left4me-overlay, and makes all overlay
content (workshop + script-built) consistent on-disk.
Verified on left4.me kernel 6.12.86 that the kernel idmap propagates
through plain re-bind, so systemd-run's BindPaths can wrap a
pre-created idmapped staging path.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
