RIBBON_COLLIDER_GIVE_M

Default collider give: comfortably past the sagitta of a RIBBON_STEP_M facet at the tightest curvature a route reaches (a hairpin near 6 m radius: 2² / (8 · 6) ≈ 0.08), because a give that only just covers the facet error still brushes the character at every ridge — felt as braking on exactly the curves a route wants taken at speed. Small enough that nothing passes through the gap: it is backed by solid hull immediately beneath, and only the top eases — sides and underside collide exactly where they are drawn.