geometry.face.absorb: tiny and sliver faces into a neighbour (#506)

A face merge may keep one of its faces' names (Merge::into, model
FaceMerge::into): absorbing a tiny face leaves the neighbour by its own
name, so sets on it still select it. Shape::absorbing_neighbour finds
the face a tiny one shares the longest edges with. geometry.face.absorb
absorbs one face (into a named or the best neighbour) or, from_check,
every small and sliver face the last geometry.check marked; check marks
now carry the small face they found.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UhhZMBTviDQxZvwnyP89fo

docs/features.md

@@ -6,7 +6,7 @@ Every entry is a toolbar button. **Ready** entries run their command; **coming s
 shown greyed with the roadmap milestone that brings them (ROADMAP.md). Scripts, the command line,
 the control channel and AI agents over MCP (docs/mcp.md) run the same commands.
 
-79 ready, 38 coming soon.
+80 ready, 38 coming soon.
 
 ## Geometry
 
@@ -23,6 +23,7 @@ the control channel and AI agents over MCP (docs/mcp.md) run the same commands.
 | Prepare | Datum Point — A datum point: coordinates, a mesh vertex, along an edge, a face's centre, an axis through a plane | ready | `geometry.datum.point`, (`geometry.datum.point.edit`) |
 | Prepare | Partition — Cut bodies into cells by a datum plane; the two faces of each cut are paired by name | ready | `geometry.partition`, (`geometry.partition.delete`), (`geometry.partition.suppress`) |
 | Prepare | Merge Faces — Mesh adjacent faces as one (virtual topology): a fillet in pieces, a face split by an imprint; the B-rep is unchanged | ready | `geometry.faces.merge`, (`geometry.faces.merge.delete`) |
+| Prepare | Absorb Faces — Absorb tiny and sliver faces into a neighbour for meshing, one picked or every one Check Geometry found | ready | `geometry.face.absorb` |
 | Prepare | Midsurface — Extract midsurfaces of thin parts for shell meshes | coming soon (M8) |  |
 
 ## Mesh