#124 twist-sign VERIFIED correct (live missile bench) + the rig to do it

The frame-adapter's inferred twist-sign flip (SelectSlice theta -= twist,
vs the binary's += pre-reflection) was the last unverified half of #124 --
every earlier probe ran at twist 0.  Bench: stationary madcat target with
the torso PINNED at 0 / +140 / -140 deg, LRM salvos from a fixed shooter
(missiles = the authentic cylinder path; the binary DROPPED zone -1 beam
damage).  Result: slice picks track the physically-facing flank in BOTH
directions (twist-left -> right-family zones for left-flank impacts,
twist-right -> left-family), deterministic, wrong-sign outcome (slice 7
vs observed slice 1) clearly excluded.  No game-code change needed.

Instrumentation added (all env-gated):
- torso.cpp BT_FORCE_TWIST=<-1..1>: HOLD the sim's analogTwistAxis (the
  input-level pin was dead -- live input rides the CONTROLS.MAP device
  push, and Basic mode auto-centers; sim-level is plumbing-independent).
- dmgtable.cpp [slice] line: rot flag, live twist, thetaIn/thetaAdj,
  chosen slice -- the weighted leaf roll made zone-only logs ambiguous.
- [dmgresolve] now names the zone (BTMechZoneSegAndName).
- mech4.cpp BT_FORCE_TWIST input pin + one-shot mode cycle (kept as doc
  of the dead path), mechmppr [mppr] mode probe.
- scratchpad/night11/twistsign.sh: the 3-config bench.

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

game/reconstructed/torso.cpp

@@ -587,6 +587,23 @@ void
 		static int s_sweep = 0;
 		analogTwistAxis = ((++s_sweep / 90) & 1) ? -1.0f : 1.0f;	// +/- every ~90 frames
 	}
+	// #124 twist-sign bench (BT_FORCE_TWIST=<-1..1>): HOLD the analog axis at a
+	// constant (the sweep above alternates) -- the sim integrates currentTwist
+	// to the per-mech limit and stays, giving the cylinder-table bench a known
+	// twist state at the SIM level, independent of the input plumbing.
+	{
+		static float s_forceTwist = -2.0f;
+		if (s_forceTwist < -1.5f)
+		{
+			const char *ft = getenv("BT_FORCE_TWIST");
+			s_forceTwist = ft ? (float)atof(ft) : -3.0f;
+		}
+		if (s_forceTwist >= -1.0f)
+		{
+			effectiveTwistRate = baseTwistRate;
+			analogTwistAxis = s_forceTwist;
+		}
+	}
 
 	// TORSO GATE PROBE (BT_TORSO_LOG): why is the twist rate zero?
 	if (getenv("BT_TORSO_LOG"))