Rear-fire + look views (task #68): the pod's rear arsenal reconstructed

The user's tip ("some mechs actually do fire backward") checks out end to
end.  Binary ground truth [T1]:
- weapon+0x334 (attr 0x1B "RearFiring"): the ctor tests the MOUNT SEGMENT's
  page name for the marker 'b' (@0x511aa2, part_013.c:6913-6930) -- the back
  gun ports sitelbgunport/siterbgunport.  The old reading ("EXT in the
  weapon model name") was a double misread (wrong string, wrong name).
- mech+0x410 (attr id 50 "RearFiring"; the old `stateFlags` label): the ctor
  ORs every weapon's flag (part_012.c:10220) -- "carries a rear arsenal".
- The mapper's five-state LOOK machine (part_013.c:396-459): on a state
  change it re-aims the eyepoint (mech+0x360 = EyepointRotation -- consumed
  by DPLEyeRenderable, already live in the port) and re-arms each weapon's
  viewFireEnable(+0x3E0): FORWARD view = the non-rear weapons, LOOK-BACK
  (yaw pi + lookBackAngle pitch) = the REAR-mounted ones, side/down = none.
  +0x3E0 is the same flag the emitter's Loaded->Firing gate reads (the old
  `useConfiguredPip` label) -- pips and fire permission both follow the view.

Port: rearFiring derived from the mount segment name (BTWeaponMountIsRear);
mech rearFiring ORed in the roster pass (the old SubProxy::IsDerivedFrom
stub returned 0 -- that loop never ran; now bridged through
BTWeaponIsRearFiring, which also fixes the weaponRoster fill); the look
commit is LIVE (BTCommitLookState: eyepoint EulerAngles from the authored
per-mech look angles -- now real members, were Wword scratch parks -- +
per-weapon view enables); MissileLauncher/ProjectileWeapon FireWeapon gate
on viewFireEnable like the emitter; RearFiring attrs (mech + weapon) bind
real members.  Keyboard: HOLD 'V' = the pod's rear-view button.

Live-verified on the default blackhawk: ERMLaser_2 -> siterbgunport rear=1,
ERMLaser_3 -> sitelbgunport rear=1, PPCs/SRMs/torso mounts forward -- the
blackhawk authors TWO REAR LASERS (owens also has back ports).  [rearfire]
trace under BT_PROJ_LOG.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

game/reconstructed/mechmppr.cpp

@@ -697,6 +697,12 @@ void
 			}
 			throttlePosition = (key_throttle >= 0.0f) ? key_throttle : -key_throttle;
 			reverseThrust    = (key_throttle < 0.0f) ? 1 : 0;
+			// (task #68) look-behind: hold 'V' = the pod's rear-view button.
+			// (The other look buttons stay unbound on the keyboard rig.)
+			{
+				extern int gBTLookBehind;
+				lookBehind = gBTLookBehind;
+			}
 			// CONTROL-MODE AXIS ROUTING (2026-07-13, the pod mapping): in
 			// BASIC the stick steers the legs (turn) and the torso auto-
 			// centers; in STANDARD/VETERAN the stick is the TORSO (free aim /
@@ -893,14 +899,16 @@ void
 
 	if (lookState != previousLookState)
 	{
-		// TODO(look-eyepoint): the commit block below writes the eyepoint pose at
-		// binary offsets whose Mech-member mapping is CONFLICTED (mech+0x360 is
-		// claimed by mechName, +0x410 by stateFlags, +0x7bc by weaponRoster --
-		// and the old draft even routed them through the TORSO pointer).  Arbitrate
-		// those labels against the raw before enabling; the port has no eyepoint
-		// consumer yet.  Look-state SELECTION above stays live (this-only).
-		DEBUG_STREAM << "[mppr] look state -> " << lookState
-			<< " (eyepoint commit deferred)\n" << std::flush;
+		// (task #68) the look commit is LIVE: the conflicted labels are
+		// arbitrated (mech+0x360 = EyepointRotation -- the eye renderable
+		// consumes it; +0x410 = RearFiring; the +0x7bc children = the WEAPON
+		// roster, not cameras).  BTCommitLookState (mech4.cpp complete-type
+		// TU) re-aims the eyepoint and re-arms each weapon's viewFireEnable:
+		// forward view = the non-rear weapons, LOOK-BACK = the rear-mounted
+		// ones, side/down = none.
+		extern void BTCommitLookState(void *mech, int look_state);
+		BTCommitLookState((void *)mech, (int)lookState);
+		DEBUG_STREAM << "[mppr] look state -> " << lookState << "\n" << std::flush;
 	}
 	else if (0)		// DEFERRED body (kept for the reconstruction record)
 	{