tendril: lightmap the tessellated cave tunnel
The tunnel Model carries a Tessellation component, and until the lightmap
UV set became a stream the tessellation pass produces, its runtime output
reached the bake with tiled uv0 only — bakeAll routed it to the probe
field while the other 78 rock receivers took per-texel lightmaps.
Its unwrapped uv1 now survives tessellation, so the bake resolves it as a
lightmap receiver: 1024 square, 87012 valid texels, baked at the same
texelsPerMeter 16 / samples 32 / intensity 2.5 as the rest of the set.
The cave now reads 79/79 static surfaces covered.