Create room 006 (Cave Entrance) and wire to room 005

- Added kq4_006_cave_entrance scene with west exit to room 005
- Updated room 005 to include target UID for room 006 transition
- Room 006 south exit to room 012 omitted (room 012 doesn't exist yet)
- Both transitions validated with exit checker

scenes/kq4_006_cave_entrance/kq4_placeholder_template.gd.uid

@@ -0,0 +1 @@
+uid://bk8q2nad4pu44