[WIP] Add UV parametric tessellation for conical surface faces

[Claude]

Thanks for asking me to work on this. I will get started on it and keep this PR's description up to date as I form a plan and make progress.

---

This section details on the original issue you should resolve

<issue_title>tess: UV parametric tessellation for CONICAL_SURFACE faces</issue_title>
<issue_description>## Problem

22 bracket faces use CONICAL_SURFACE (tapered transitions between features of different radii). All fall through to the flat-projection path and are tessellated as flat polygons — conical geometry is flattened instead of preserving the taper angle.

What the fix looks like

Add try_tessellate_conical, analogous to try_tessellate_cylindrical:

1. Detect CONICAL_SURFACE — parse axis, radius (at v=0), and semi_angle.
2. Sample the boundary to find the v-range (distance along the cone's slant).
3. Determine the angular u-range from the boundary points — check for a closed-circle edge to detect full-revolution cones vs. partial arcs.
4. For full-revolution cones: generate a UV grid (u = angle 0..2π, v = slant distance), evaluate ConicalSurface::point(u, v) for each grid vertex.
5. For partial cones: invert boundary points to UV, triangulate in UV, lift back.

The parametric equation is already implemented in ConicalSurface::point:

P(u,v) = origin + (radius + v·sin(φ))·(cos(u)·x + sin(u)·y) + v·cos(φ)·z

Affected code

• crates/kofem-geom/src/tess/mod.rs — add try_tessellate_conical
• crates/kofem-geom/src/geom/surface.rs — ConicalSurface::point already implemented

Impact

22 faces — conical transitions and chamfers on the bracket.</issue_description>

Comments on the Issue (you are @claude[agent] in this section)