AST-driven, body-identical move of 359 GatewayRunner methods into cohesive
mixin modules (gateway/run_{voice,adapters,topics,turn,shutdown,busy,
config_loaders,startup,watchers,notifications,inbound,goals,agent_cache}.py)
plus TurnRunner -> gateway/run_turn_runner.py. run.py-internal symbols are
imported lazily inside method bodies so patch('gateway.run.X') keeps
intercepting; neutral deps are top-level; logger name stays 'gateway.run'.
_UNSET moved to leaf gateway/run_common.py (def-time default-arg sentinel).
Whole-module inspect.getsource(gateway_run) AST-walker tests repointed to
the module that now holds the walked code.