fix: Godot 4.2.1 compat and map builder fixes

- Fix tab character in _build_elevated_walkways() call (line 63)
- Fix untyped 'pos' variable in grapple pillar loop (line 376)
- Remove fog_sky_affinity (Godot 4.3+ only property)
- Replace preload() with load() for runtime script loading
- Replace 'is DoubleBarrelShotgun' type check with duck-typing
- Fix 'is not OfflineMultiplayerPeer' syntax in grenade spawn
- Replace absf() with abs() in state_machine, state_air, state_ground
- Update test_level.tscn to remove stale UID reference

All fixes verified: PARSE OK and scene runs without script errors
on Godot 4.2.1 headless.

movement/states/state_air.gd

@@ -145,7 +145,7 @@ func update(delta: float) -> void:
 			
 			# Require looking mostly along the wall (angle > 41 degrees from normal)
 			# and inputting mostly along the wall (angle > 31 degrees from normal, allows W+A/D diagonally into wall)
-			if absf(h_look.dot(wall_n)) < 0.75 and absf(wish_dir.dot(wall_n)) < 0.85:
+			if abs(h_look.dot(wall_n)) < 0.75 and abs(wish_dir.dot(wall_n)) < 0.85:
 				machine.switch_to("wall_run")
 				return