Kind of after the battle but... Changing orbits could work.
Could a sentient planet change its density by moving "inner" magma from place to place enough for it to change orbits ? Theoretically, with no friction due to being in space, moving its mass to the "back" would make it move to the "front", and placing it back would stop it.
Another idea would be to mind-control all of its biomass somehow to achieve a similar result, but biomass is really tiny compared to a planet's mass.
Some "plants" which store light and then convert it into cinetic energy could work. Then release energy at day to make the planet move "warmer", at night for "colder".
Without changing positions, space is cold, but not quite at 0° K. It's about 2°K if I remember well. The planet could absorb ambient heat to get an higher temperature. It would need to harvest quite a large area however.
Last idea, similar to the "uranium on fire" in concept. It would be limited in time, but to heat up, it could manipulate components in its core to create endothermic / exothermic chemical reactions on a planetary scale.
