#52 SKATE detector (ungated field forensic) -- negative-verified; local repro eludes

The night-12 field logs eliminated record starvation (zero [ghost] during
three observed skating windows), so the bug lives in gait APPLICATION on
peers.  This adds the [skate] detector to the death-handler tick: a
replicant moving >0.08 u/frame for 90+ frames with BOTH animation
channels idle (legCycleSpeed + bodyCycleSpeed ~ 0) logs one line per
episode + a SKATE matchlog record carrying the discriminating inputs
(legCyc/bodyCyc/cmdSpd/destroyed/mode).

Honest history: the first build keyed on legCycleSpeed alone and
false-fired on every healthy movement phase -- the current peer
architecture poses joints from the BODY channel (s_peerLegCh=0,
AdvanceBodyAnimation mj=1), so legCycleSpeed==0 is NORMAL there.  Caught
same-session by the [gimpfeed] silence (AdvanceLegAnimation never runs
on peers); corrected to channel-agnostic before anything shipped.

Bench (skatebench2.sh, 2-node, autodrive walker + kill every ~40s):
7 death/respawn cycles, ZERO skate hits either side -- no false fires,
and light local conditions do NOT reproduce the field skating.  Next
provocations: leg-GIMPED walker (the #82 family transition) and 6-player
load; otherwise the detector rides the next cut and the field names the
failing case for us.

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

game/reconstructed/mechdmg.cpp

@@ -1206,7 +1206,8 @@ void
 }
 
 MechDeathHandler::MechDeathHandler(Mech *mech)			// @0042a984
-	: owner(mech), prevMode(0), ghostFrames(0), ghostLogged(0)
+	: owner(mech), prevMode(0), ghostFrames(0), ghostLogged(0),
+	  skatePrevX(0.0f), skatePrevZ(0.0f), skateFrames(0), skateLogged(0)
 {
 	// per-zone last-damage cache, zeroed (binary this[0x10], size mech+0x11c).
 	int count = (mech != 0 && mech->damageZoneCount > 0) ? mech->damageZoneCount : 0;
@@ -1229,6 +1230,64 @@ void
 	if (owner == 0)
 		return;
 
+	// #52 SKATE DETECTOR (PORT, ungated -- the night-12 forensic): a REPLICANT
+	// whose position advances while its LEG CHANNEL is not cycling is the
+	// field "skating" signature.  One line per episode, carrying the three
+	// inputs that split the failure: bodyTargetSpeed (the replicated commanded
+	// speed the leg SM feeds from -- ~0 means the RECORD side starved the
+	// gait), legCycleSpeed (~0 with a live demand means the SM is STUCK), and
+	// IsMechDestroyed (1 means the gait feed block was SKIPPED -- the stale
+	// post-respawn flag suspect).  ~90 frames of sustained skate to trip; the
+	// threshold 0.08 u/frame ~ 2.4 u/s at 30 fps, well above reckoner jitter.
+	if (owner->GetInstance() == Entity::ReplicantInstance)
+	{
+		const float px = (float)owner->localOrigin.linearPosition.x;
+		const float pz = (float)owner->localOrigin.linearPosition.z;
+		const float dx = px - skatePrevX, dz = pz - skatePrevZ;
+		const float step = sqrtf(dx * dx + dz * dz);
+		skatePrevX = px; skatePrevZ = pz;
+		// CHANNEL-AGNOSTIC (corrected same-day): the peer's joints are posed by
+		// the BODY channel in the current authentic architecture (mech4
+		// s_peerLegCh=0 -> AdvanceBodyAnimation mj=1), so legCycleSpeed==0 is
+		// NORMAL there -- the first detector build false-fired on every healthy
+		// movement phase.  Skating = moving with BOTH channels idle.
+		const float cyc = fabsf((float)owner->legCycleSpeed)
+			+ fabsf((float)owner->bodyCycleSpeed);
+		const int movingNoLegs = (step > 0.08f && step < 5.0f	// 5+: teleport/warp
+			&& cyc < 0.05f) ? 1 : 0;
+		if (movingNoLegs)
+		{
+			if (++skateFrames > 90 && !skateLogged)
+			{
+				skateLogged = 1;
+				DEBUG_STREAM << "[skate] replicant " << owner->GetEntityID()
+					<< " SKATING: " << skateFrames << " frames moving ("
+					<< step << " u/frame) with legCyc="
+					<< (float)owner->legCycleSpeed
+					<< " bodyCyc=" << (float)owner->bodyCycleSpeed
+					<< " bodyTargetSpeed=" << (float)owner->bodyTargetSpeed
+					<< " destroyed=" << (int)owner->IsMechDestroyed()
+					<< " mode=" << (int)owner->MovementMode()
+					<< " at (" << px << "," << pz << ")\n" << std::flush;
+				if (BTMatchLogActive())
+					BTMatchLog("SKATE", "mech=%d:%d frames=%d step=%.3f cyc=%.3f "
+						"cmdSpd=%.2f destroyed=%d mode=%d x=%.1f z=%.1f",
+						BTMatchHostOf(owner->GetEntityID()), (int)owner->GetEntityID(),
+						skateFrames, step, cyc,
+						(float)owner->bodyTargetSpeed,
+						(int)owner->IsMechDestroyed(), (int)owner->MovementMode(),
+						px, pz);
+			}
+		}
+		else if (skateFrames > 0)
+		{
+			if (skateLogged)
+				DEBUG_STREAM << "[skate] replicant " << owner->GetEntityID()
+					<< " recovered after " << skateFrames << " frames\n" << std::flush;
+			skateFrames = 0; skateLogged = 0;
+		}
+	}
+
 	// #108 GHOST DETECTOR (PORT, ungated -- the night-9 forensic): a visible
 	// REPLICANT that stops receiving update records is exactly what "everyone
 	// shoots thin air" looks like from the other side.  ReadUpdateRecord