Flatten diagonal wall QA/WS floordata collision to the exposed triangle

[Copilot]

Tilting the QA side of a diagonal wall could leak its slope into the nominally flat lower triangle, producing invalid wall collision and letting Lara slide into void space. The same compiler path also affected the WS side, so both floor and ceiling diagonal-wall collision needed to preserve the flat exposed half.

• Compiler collision shape

  • Adjust LevelCompilerTombEngine.RoomSectorShape for diagonal wall sectors so QA/WS collision is flattened to the visible flat triangle.
  • Adjust LevelCompilerClassicTR.RoomSectorShape the same way so the legacy/classic floordata compiler no longer carries the hidden sloped half into collision.
  • Zero out the diagonal step for wall collision after flattening, preventing the hidden sloped half from influencing TEN and classic floordata collision.
  • Leave non-wall diagonal sectors unchanged.

• Documented engine/editor mismatch

  • Added in-code notes describing the current tilting hack: editor geometry can still carry tilt on the hidden half, but wall collision currently exposes only the flat triangle until extra probes exist to represent both halves.

• Regression coverage

  • Added focused tests for all four diagonal split orientations.
  • Covered both floor and ceiling wall collision paths for the TEN and classic compiler implementations.
  • Kept a control case to ensure regular diagonal split sectors keep their original behavior.

if (wall && surface.DiagonalSplit != DiagonalSplit.None)
{
    FlattenDiagonalWallPart(surface.DiagonalSplit, ref heightXnZn, ref heightXnZp, ref heightXpZn, ref heightXpZp);
    diagonalStep = 0;
}

[Nickelony]

@copilot What about the classic, legacy compiler? You seem to have only fixed the TEN compiler.

[Copilot]

@copilot What about the classic, legacy compiler? You seem to have only fixed the TEN compiler.

Handled in 8bf2b29. The classic/legacy compiler had the same diagonal wall QA/WS collision shape issue, so I applied the same flattening there and extended the regression tests to cover both classic and TEN.