An actor gains `outline` (metres of rim) and `ocol` (its colour). The pass draws
the model a second time with its vertices pushed out along their normals and its
front faces culled, so only the far side of the swollen shell survives - a
silhouette exactly `outline` metres wide. It is depth-tested against the scene,
so anything standing in front of the actor hides the rim too.
skin.vert grows an OUTLINE path for the push; outline.frag is the flat-colour
fragment shader it pairs with.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
