The boot reconciler (`reconcile_profile_gateways`) registered every named
slot down and folded any slot's `running` intent into the root slot. The
root multiplexer never serves a `gateway.standalone` profile
(`profiles_to_serve` excludes it), so after every container restart that
profile had no gateway while the boot log claimed the root served it.
A standalone profile's slot now boots from its own intent and is kept out
of the fold; every other named slot stays registered down. The reconcile
comment and the fold notice name the exception, and the standalone docs say
its listener needs its own port beside a host gateway that enables the same
one.
`gateway.parked` is deliberately NOT consulted here: parked is orthogonal to
standalone (a host-served profile the operator took offline), the in-process
migration path (`gateway_migrate`) already leaves standalone-by-config
profiles alone, and the root multiplexer skips parked profiles itself.
(cherry picked from commit 1b28dee46d96e5509bd00b567c4658f5e47600d1)
8e9d1b90c9