feat: thinner cel outline + procedural model actually holds its weapon

Outline: the inverted-hull width was tuned when the look was heavier and
now reads as a thick marker stroke. Cut every call site to roughly a third
(characters 0.012 -> 0.004, level geometry 0.015 -> 0.005, Neon Alley's
size-scaled clamp 0.02..0.05 -> 0.007..0.018) plus the shader default, so
the ink line stays readable without fattening every silhouette.

Third-person weapon on HumanoidModel: the gun was parented to root_pivot at
a fixed (-0.15, 1.0, 0.4) — floating 40 cm off the chest while both arms
posed at it from a distance. Give the rig a real right-hand node at the end
of the forearm and hang the weapon there, so it travels with the arm. Its
aim is re-derived from the body each frame (hand_r_pivot's global basis is
copied from root_pivot), otherwise the barrel would swing around with the
arm animation. The hold pose is retuned to match: right elbow tucked at the
ribs with a level forearm, left arm crossing to the handguard.

_seat_weapon_in_hand() slides each weapon along its own barrel axis so a
plausible grip lands in the fist regardless of where the artist left the
model origin. It measures with MeshInstance3D.get_aabb(), not
mesh.get_aabb() — the FBX gun parts are skinned, so the Mesh resource still
carries bind-pose bounds tens of metres across.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

scenes/maps/level_materials.gd

@@ -98,7 +98,7 @@ static func toonify(src: Material) -> Material:
 ## Swap every mesh surface under `node` to toon shading and add an
 ## inverted-hull outline overlay. Safe on skinned meshes (material_overlay
 ## re-renders the same deformed mesh).
-static func apply_toon_recursive(node: Node, outline_width: float = 0.015) -> void:
+static func apply_toon_recursive(node: Node, outline_width: float = 0.005) -> void:
 	if node is MeshInstance3D:
 		var mi := node as MeshInstance3D
 		var surface_count: int = mi.mesh.get_surface_count() if mi.mesh else 0
@@ -112,7 +112,7 @@ static func apply_toon_recursive(node: Node, outline_width: float = 0.015) -> vo
 		apply_toon_recursive(child, outline_width)
 
 
-static func outline(width: float = 0.015) -> ShaderMaterial:
+static func outline(width: float = 0.005) -> ShaderMaterial:
 	var key := "%.4f" % width
 	if _outline_cache.has(key):
 		return _outline_cache[key]