Add patrolling enemies and link level 1 to level 2

New walker prefab (mushroom_red sprite) patrols a platform, turns at walls and ledges, drains a heart on contact and dies when stomped, bouncing the player up. Three are placed in level2. The level 2 spawn point is set to cell (7,11) so the player starts standing on the floor instead of falling in from mid-air, and level 1's LevelClear now loads level2.tscn.

scenes/prefabs/enemies/walker.tscn

@@ -0,0 +1,35 @@
+[gd_scene load_steps=5 format=3]
+
+[ext_resource type="Texture2D" path="res://assets/game/vegetation/mushroom_red.png" id="1_tex"]
+[ext_resource type="Script" path="res://scripts/walker.gd" id="2_walker"]
+
+[sub_resource type="RectangleShape2D" id="Shape_body"]
+size = Vector2(12, 16)
+
+[sub_resource type="RectangleShape2D" id="Shape_touch"]
+size = Vector2(16, 16)
+
+[node name="Walker" type="CharacterBody2D" groups=["enemy"]]
+z_index = 5
+collision_layer = 4
+collision_mask = 1
+script = ExtResource("2_walker")
+
+[node name="Sprite" type="Sprite2D" parent="."]
+texture_filter = 1
+texture = ExtResource("1_tex")
+
+[node name="Collision" type="CollisionShape2D" parent="."]
+shape = SubResource("Shape_body")
+
+[node name="FloorProbe" type="RayCast2D" parent="."]
+position = Vector2(-6, 7)
+target_position = Vector2(0, 9)
+collision_mask = 1
+
+[node name="TouchArea" type="Area2D" parent="."]
+collision_layer = 0
+collision_mask = 2
+
+[node name="TouchShape" type="CollisionShape2D" parent="TouchArea"]
+shape = SubResource("Shape_touch")