MP: the Mech-level update records @0x4a0c2c/@0x4a1232 -- all 9 types byte-exact (task #1)

- Writer transcribed from the recovered disasm; reader rewritten from
  part_012.c with every Wword absorber promoted to named engine/port members
  (updateOrigin/updateVelocity/projectedOrigin/projectedVelocity/nextUpdate/
  lastUpdate + bodyTargetSpeed/latches/alarms).  Wire sizes verified live:
  0x14/0x20/0x2c/0x78.
- movementMode UNIFIED with Simulation::simulationState (binary mech+0x40 =
  StateIndicator@0x2c currentState) -- death/limbo/airborne now replicate in
  every record header.  Three mislabels of the same binary fns retired:
  SetInstanceFlags + RequestActionFlags -> Mech::ForceUpdate (updateModel |=
  mask, 0xfe03 disabled filter); IsNetworkCopy -> IsDisabled.
- Senders wired byte-exact: gait transitions Force(8), knockdown Force(1|0x20),
  death Force(1|0x40), Reset Force(0x1f) + binary zero-set, perf-loop
  deadbands (speed type 2, orientation type 4, heat type 7).
- 2-node verified: types 2/3/4 flow while driving; kill -> type-6 record
  (simState=9) -> the OBSERVER's replicant runs the wreck sink loop with no
  double death transition; respawn 0x1f burst snaps + un-wrecks the peer;
  walking replicant un-regressed (run 12, cycle tracking); solo clean.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

game/reconstructed/btstubs.cpp

@@ -120,7 +120,7 @@ int Mech::IsAirborne()
 // that lands.  Faithful to the binary regardless.
 Logical Mech::IsDisabled()
 {
-	return (movementMode == 2 || movementMode == 9) ? True : False;
+	return (MovementMode() == 2 || MovementMode() == 9) ? True : False;
 }
 
 // mech+0x404 = the radar display scale.  Both the radar map's currentScale and