Function attachFreeControl

Attach keyboard + mouse controls to a FreeCamera. Matches Babylon.js FreeCamera input behavior:

• Mouse drag or pointer-lock: look around (yaw/pitch)
• Arrow keys / WASD: move forward/back/strafe
• PageUp/PageDown or Space/Shift: move up/down
• Inertia: movement decays smoothly (camera.inertia, default 0.9)
• Frame-rate independent: uses deltaTime from render loop

Camera stays plain data — this function reads/writes its properties. Returns a cleanup function to remove all listeners and the beforeRender hook.