feat(client): mouse-relative facing and movement (#526, D-054)

Mouse position now determines facing direction as a client-side float.
WASD remapped: W=toward cursor, S=away, A/D=strafe. Facing octant
derived from mouse angle and sent to server via SET_FACING action only
when it changes. EntityRenderer facing indicator uses continuous angle
for smooth rotation. SimBridge test mode updated to handle SetFacing.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

client/scripts/autoloads/sim_bridge.gd

@@ -258,6 +258,8 @@ static func _action_enum_to_wire(action: int) -> String:
 			return ""  # Client-only action, not part of wire protocol
 		InputMapper.Action.BUG_REPORT:
 			return ""  # Client-only action (#495), not part of wire protocol
+		InputMapper.Action.SET_FACING:
+			return "SetFacing"  # D-054: facing octant update (no movement)
 		_:
 			push_warning("SimBridge: unknown action enum %s" % action)
 			return ""
@@ -280,12 +282,18 @@ func _test_snapshot() -> Dictionary:
 			if dist <= 2 and _test_has_los(_test_player_pos, npc_pos):
 				_test_in_dialogue = true
 			continue
+		if action_name == "SetFacing":
+			# D-054: facing update handled separately — octant comes from InputMapper
+			_test_facing = InputMapper.facing_octant
+			continue
 		var delta := _action_to_delta(action_name)
 		var new_pos := _test_player_pos + delta
 		if _test_is_walkable(new_pos):
 			_test_player_pos = new_pos
 			if delta != Vector2i.ZERO:
-				_test_facing = _delta_to_facing(delta)
+				# D-054: Facing is now mouse-driven, not movement-driven.
+				# Use InputMapper's octant instead of deriving from movement delta.
+				_test_facing = InputMapper.facing_octant
 				# Walk-away dismisses dialogue (D-064)
 				if _test_in_dialogue:
 					_test_in_dialogue = false