BT410 5.3.129: shot-up muscles slow the mech -- the mobility scan lands and the mobilityScale [T1] retires

The master perf's opening scan maxes the myomer chain's speedEffect into
the mobility scale and applies it straight to the pilot's command cells:
the throttle is multiplied by it, and a scale inside the 1e-4 deadzone
zeroes the turn outright -- a mech with dead muscles cannot even pivot.
It is the same cell the duck driver already read as "the legs still work",
so that gate stops being a constant.

THE CHAIN IDENTITY IS NOW PROVEN RATHER THAN INFERRED.  My 5.3.122 note
pinned mech+0x7ac to Myomers "by adjacency to the string pool", which
nearly went wrong: the very cell the scan reads, +0x31c, is a MechWeapon
trigger over in the weapon TU.  The decisive evidence is arithmetic --
the Myomers cap-raise reads seekVoltage at +0x330 indexed by
maxSeekVoltageIndex at +0x32c, and walking our own member order backwards
from there lands speedEffect exactly on +0x31c.

The ctor's myomer sweep also carries the other half: walking the chain is
what sets the "I computed my own top speed" flag, so a mech WITH myomers
broadcasts its cap and one without adopts the streamed value.

Safe by construction against the obvious hazard: the mapper reassigns its
demands from scratch in InterpretControls, which ticks before the mech's
performance, so multiplying its cell in place cannot compound frame to
frame.

Soak: [mobility] scale 1 over 1 myomers on an undamaged bhk1 -- throttle
unscaled, drive unchanged, zero faults.

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

restoration/source410/BT/MECHMPPR.HPP

@@ -169,6 +169,24 @@
 		Scalar
 			GetTurnDemand() const	{ Check(this); return turnDemand; }
 
+		//
+		// The master perf writes the mobility scale straight into the
+		// mapper's command cells (binary @0x4a9d5d: throttle *= scale, and
+		// a scale inside the 1e-4 deadzone zeroes the turn outright -- a
+		// mech with dead myomers cannot even pivot).  Applied here so the
+		// cells stay owned by the mapper.
+		//
+		void
+			ApplyMobilityScale(Scalar scale)
+				{
+					Check(this);
+					speedDemand *= scale;
+					if (scale <= 0.0001f && scale >= -0.0001f)
+					{
+						turnDemand = 0.0f;
+					}
+				}
+
 		//
 		// The LIMP machines write the demand cell DOWN to the damaged side's
 		// speed cap (binary GimpLegClipFinished @004a7970 preamble writes