Aim ray follows the torso elevation (the boresight leveling erased it)

Follow-through on the pitch fix: the view pitched but shots still flew
level (user report).  Cause: the task-#48 AIM BORESIGHT leveling in the
eye's aim-camera publish (L4VIDRND) strips ALL pitch from the pick-ray
direction -- correct for the TERRAIN body pitch it was built against, but
it also erased the pilot's deliberate R/F elevation.

Fix: mech4's per-frame eye compose publishes the torso elevation
(gBTEyeElev); the publisher re-applies it onto the LEVELED forward
(fwd = (cos e * level, sin e)) before building the basis -- terrain pitch
stays stripped, the deliberate aim survives into BTGetAimRay.  Sign
matches the pixel-calibrated view compose (+ = up).

Harness evidence: pinned-down elevation visibly pitches the chase eye
into the terrain (the ray basis moves); a full headless aimed-kill could
not be driven (the autofire gate needs a designated target and the
random spawns wedged short of the truck row) -- aim-at-truck kill needs
the human pass.  Awaiting human verification (issue #8).

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

game/reconstructed/mech4.cpp

@@ -4966,6 +4966,12 @@ void
 					Radian(Radian::Normalize(gBTLookPitch + elev)),
 					Radian(Radian::Normalize(gBTLookYaw)),
 					Radian(0.0f));
+				// ...and the AIM RAY: the boresight publisher (L4VIDRND task
+				// #48) LEVELS the view direction (drops terrain body pitch) --
+				// publish the deliberate elevation so it re-applies onto the
+				// leveled boresight (else shots fire level over low targets).
+				extern float gBTEyeElev;
+				gBTEyeElev = elev;
 			}
 		}