SetMappingSubsystem installs the control mapper into roster slot 0 (the streamed
control-mapping binds DirectMappings to subsystemID 0). MechControlsMapper ctor
constructs (per-frame InterpretControls deferred to phase 5). With RIO controls,
MakeViewpointEntity now builds the MechRIOMapper, installs it, and gets PAST the
controls check -- the mech constructs AND links as the viewpoint entity. Boot now
advances into the mission-startup / control-binding path (next: a real NULL-deref
there, deeper than the staged Fails). BT: 42 ok.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>