tendril: bake the cave tunnel at 2048, drop repro leftovers
The tunnel carries 3107 m2 of surface, more than the rest of the cave set
combined, and its lightmap was the coarsest of the 79 receivers at roughly
12 cm per effective texel while every prop around it sat at 3-4 cm. It now
bakes at 2048 with 64 samples: 917,767 valid texels, 4x the density, on its
own atlas page. setupPersistentGi splits its pass from the props so the two
carry different resolutions.
Also removes repro_a1 / repro_a2 / repro_b, three component-less entities
left in the scene by an earlier investigation.