setup_logging(mode="gateway") binds agent.log / errors.log / gateway.log
to the launch home, so under multiplex_profiles every secondary profile's
records (emitted inside _profile_runtime_scope) landed in the DEFAULT
profile's files. Main already has the routing primitives from #99440
(record.hermes_home factory + _ProfileRoutingFileHandler +
enable_profile_log_routing) but only the Desktop cron ticker used them.
Enable them at gateway startup for the served profile set; single-profile
gateways are untouched (routing is a no-op below two homes).
Supersedes #84954, which introduced a parallel routing mechanism; the
cross-profile isolation test is translated from its suite.
Co-authored-by: Michał Dziwisz <michal@dziwisz.net>
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