perf(visualization): skip bottom faces in GPU index buffer and optimize highlighting

Skip bottom face indices in the treemap rendering (never visible), reducing
GPU index count by ~17%. Restore bottom faces in the 3D print export to keep
meshes watertight. Cache highlighted/dimmed color vectors on CodeMapBuilding
to avoid repeated HSL conversions. Replace highlighted-building array with a
Set for O(1) lookups. Batch render calls via requestAnimationFrame. Update
label line animation to modify vertices in-place. Fix edge preview effect to
respect user-chosen count of 0.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>