core v0.9.0

Remote motion controllers for games that show other players as locally simulated copies, and launch-time names
that stay launch-time. New features, so a minor release. No breaking changes; the wire protocol version stays 7.

• net/remote_motion.h (pure, no game calls):
  • LocomotionController: from the remote target (position, velocity, heading, sprint / in-air flags) and the
    copy's reported position, a gait (stand / walk / run / sprint, with hysteresis), a speed multiplier for the
    game's own locomotion (the walk/run/sprint speed at multiplier 1 is calibrated at run time from the copy's
    measured speed, so a game's nominal speeds need not be known), a walk point ahead along the wanted velocity (or
    the spot itself when the remote player stands) and when to re-aim it, a position fix that stays small (only the
    error beyond 0.9 m is nudged, 2/s; a snap beyond 3.5 m / 3 m height, or when the copy is blocked), and a
    rate-limited turn toward the remote heading while standing. Meant to replace "pull the copy toward the target
    every tick", which slides its feet.
  • VehicleController: keeps a car copy on its target while its own physics carries it (blended position and
    rotation correction; nothing applied while it is on target, so the game's own animations on a standing car are
    not disturbed), switches to pinning it every tick when its physics does not keep up (the game's teleport zeroed
    its speed), runs off or stays more than 1.5 m off for 1.5 s, snaps on teleports / beyond 4 m, and governs the throttle (none while the copy is faster
    than its target).
  • PackSnorm8 / PackUnorm8 (and unpack) for control values on the wire; Nlerp for quaternions.
• Config::GetFileString(key): the value from the settings file (or a saved Set), ignoring launch overrides.
• CO-OP SETTINGS > NAME: the box now shows (and SAVE writes) the name saved in the settings, not a --name given on
  the command line for one run (a test's --name Host was saved for good by pressing SAVE). The log says when the
  name comes from the command line, so the Steam name is not used.
• core_version.h: the minor number said 7 since v0.8.0; now 0.9.0 throughout.
• Tests: net_motion (quantisation round trips and clamping, nlerp sign fix; the locomotion controller against a
  simulated AI walker whose real speeds differ from the first guess: the gait follows stand / walk / run / sprint /
  turn / stop, no snaps, average error 0.14 m, no position nudges in steady motion, speeds calibrated to within 2 %, a
  blocked copy snapped after 2 s, a 180 degree standing turn in 0.43 s; the vehicle controller with a physics that
  carries the car (blended, 0.02 m) and one whose teleport zeroes its speed (pinned after 1.5 s), snap, overspeed,
  runaway, lag); config_set checks GetFileString.