fix(characters): rig-independent weapon mount, measured facing, revert Miku

WEAPON MOUNT, all models. set_weapon() seated the gun with a fixed
rotation_degrees = (0, 90, -90). A bone attachment is expressed in the
BONE's axes and no two rigs agree on those, so one constant mounted the
weapon differently on every character. It never needed to be right: the
pose layer aims the gun by rotating the wrist until the weapon's forward
lies on the aim line, so the identity means "forward is the hand bone's
-Z", which is true on any rig, and the wrist absorbs the roll. The grip
now sits at the bone origin, so the gun is in the hand rather than at an
offset from a differently-oriented bone. Verified by render on kiyoko:
rifle shouldered, both hands on it.

FACING. flatten_and_scale() now measures toes-versus-ankles and snaps the
character to face Blender -Y, the convention the runtime's blanket flip is
built around. Kiyoko was 180 degrees off. Snapped to the nearest quarter
turn so splayed feet in a rest pose are not read as a turned character.

MIKU. Re-imported without --grow-cloth. Her grown hair chains were the
cause of the stretching: cloth_bones.py clears a vertex's body weights and
re-assigns it to the fitted polyline, so a poor fit does not degrade to
"stiff", it degrades to "torn". She now has no hair simulation — stiff but
correct — until that tool blends against the weights it replaces instead
of destroying them.

ARIA'S SKIRT IS NOT SIMULATED. Worth recording plainly, because it looks
better than Taila's and the obvious conclusion is the wrong one: aria has
ZERO cloth chains. Her skirt never clips because it is rigidly skinned and
follows the legs it is weighted to. There is nothing to port to Taila
except switching her simulation off.

Co-Authored-By: Claude Opus 5 <[email protected]>

characters/skinned_player_model.gd

@@ -908,17 +908,27 @@ func set_weapon(script_path: String) -> void:
 		# (weapon swap while toggled), else the new weapon comes up invisible.
 		if (shadows_only or first_person_mode) and not _owner_visible:
 			_set_shadows_recursive(w)
-		# Undo the first-person viewmodel placement from the weapon's _ready:
-		# lie along the hand's grip, scaled down to character proportions.
-		w.position = Vector3(-0.02, 0.07, 0.0)
-		w.rotation_degrees = Vector3(0, 90, -90)
-		w.scale = Vector3(1.0, 1.0, 1.0)
-		# Tell the pose layer the gun's axes in hand-bone space so it can
-		# aim the wrist to point the muzzle exactly where the player looks.
+		# Seat the weapon in the hand with NO hand-relative rotation.
+		#
+		# There used to be a fixed `rotation_degrees = (0, 90, -90)` here, which
+		# is the offset that happens to be right for the library's own DEF-hand.R
+		# and is wrong for every rig whose hand bone has a different roll. A bone
+		# attachment is expressed in the BONE's axes, and no two rigs agree on
+		# those, so a constant here mounts the gun differently on every character
+		# — which is what "the hand mount points are totally wrong on all models"
+		# was.
+		#
+		# It does not need to be right, because the pose layer aims the gun by
+		# rotating the WRIST until the weapon's forward axis lies on the aim line
+		# (see _apply_rifle_hold). Handing it the identity means "the gun's
+		# forward is the hand bone's -Z", which is true by construction on any
+		# rig, and the wrist then absorbs whatever that bone's roll happens to be.
+		# The grip is placed at the bone's origin below, so the gun sits IN the
+		# hand rather than at a fixed offset from a differently-oriented bone.
+		w.transform = Transform3D.IDENTITY
 		if _pose_mod:
-			var b: Basis = w.transform.basis.orthonormalized()
-			_pose_mod.gun_fwd_hand = b * Vector3(0, 0, -1)
-			_pose_mod.gun_up_hand = b * Vector3(0, 1, 0)
+			_pose_mod.gun_fwd_hand = Vector3(0, 0, -1)
+			_pose_mod.gun_up_hand = Vector3(0, 1, 0)
 			_measure_weapon(w)
 	)