Purely additive: creates the synthetic outdoor cell node that will serve as the
flood-graph root for the unified render pipeline. Each nearby building's exit
portal (OtherCellId==0xFFFF) is reversed into a portal pointing back into the
building, with its polygon transformed to world space and InsideSide flipped so
the outdoor half-space is "inside" the node. WorldTransform=Identity (portals in
world space). Mirrors retail's outdoor landcell that DrawInside(viewer_cell)
roots at (SmartBox::RenderNormalMode, decomp pc:92635). Nothing consumes this
yet — consumer wiring is Task 2.
2 new tests, 212 total passing, 0 regressions.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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