Surface bodies: Patch, Stitch, Trim and Thicken

Kernel (surfaces):
- Bodies with an open shell are surface bodies (Body::is_surface).
- patch_region: a planar patch of a sketch region. patch_edges: a planar
  patch filling a closed loop of a body's edges.
- copy_faces: faces copied out as a surface.
- stitch: sew surfaces along coinciding edges, turning faces to agree; the
  result is a solid when it closes.
- trim: cut a surface by a plane or face and keep one side.
- thicken: offset planar and circular-cylindrical faces along their
  normals (one side or symmetric) into a solid. Plane copies slide;
  cylinder copies scale about the axis, exact for NURBS circles. Free
  edges get ruled walls. Faces meeting at a sharp edge are refused.

Doc features Patch, Stitch, Thicken (with operations) and SurfaceTrim;
engine commands FusionSurfacePatchCommand, FusionSurfaceStitchCommand,
FusionSurfaceThickenCommand and FusionSurfaceTrimCommand.

Tests (volumes):
- A 10x10 patch thickened by 2 gives 200, also symmetric.
- Half a cylinder side thickened outward gives half a ring; both halves
  inward give the full ring.
- Six faces of a box stitched back give 6000; an open box with its top
  patched from the edges, stitched, gives 6000.
- Trim keeps 30 or 70 of 100.
- Engine: patch, trim, thicken gives 140.

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01AS5Tn3xieewUSg3uxrMVdL

docs/parity.md

@@ -2,13 +2,13 @@
 
 Generated by `cargo xtask parity` from `xtask/data/fusion-catalog.tsv` (the toolbar commands of Fusion's Design workspace, ids and names only) and the live command registry (`solvecraft-cli commands`). A command counts as live when SolveCraft registers the same command id. This measures breadth, not depth; see ROADMAP.md and docs/oracle.md for depth.
 
-**In scope (SOLID, SKETCH, ASSEMBLY, SHEET METAL, PLASTIC enclosure subset): 278 / 541 commands live (51%).** SOLID + SKETCH: 167 / 291 (57%). Registered commands: 276.
+**In scope (SOLID, SKETCH, ASSEMBLY, SHEET METAL, PLASTIC enclosure subset): 279 / 541 commands live (52%).** SOLID + SKETCH: 168 / 291 (58%). Registered commands: 280.
 
-Deferred until further notice (not in the in-scope figure): MESH, FORM, SURFACE beyond what solids need, PCB, render, animation, simulation, manufacture, drawings, MANAGE, UTILITIES and the rest of PLASTIC. All Design tabs together: 494 / 1175 (42%).
+Deferred until further notice (not in the in-scope figure): MESH, FORM, SURFACE beyond what solids need, PCB, render, animation, simulation, manufacture, drawings, MANAGE, UTILITIES and the rest of PLASTIC. All Design tabs together: 500 / 1175 (43%).
 
 | Tab | Panel | Live | Total | % |
 |---|---|---:|---:|---:|
-| SOLID | CREATE | 22 | 35 | 63% |
+| SOLID | CREATE | 23 | 35 | 66% |
 | SOLID | MODIFY | 18 | 32 | 56% |
 | SOLID | ASSEMBLE | 12 | 21 | 57% |
 | SOLID | CONFIGURE | 2 | 3 | 67% |
@@ -53,8 +53,8 @@ Deferred until further notice (not in the in-scope figure): MESH, FORM, SURFACE
 
 | Tab | Panel | Live | Total | % |
 |---|---|---:|---:|---:|
-| SURFACE | CREATE | 7 | 25 | 28% |
-| SURFACE | MODIFY | 13 | 26 | 50% |
+| SURFACE | CREATE | 9 | 25 | 36% |
+| SURFACE | MODIFY | 15 | 26 | 58% |
 | SURFACE | ASSEMBLE | 11 | 20 | 55% |
 | SURFACE | CONFIGURE | 2 | 3 | 67% |
 | SURFACE | CONSTRUCT | 2 | 20 | 10% |
@@ -84,7 +84,7 @@ Deferred until further notice (not in the in-scope figure): MESH, FORM, SURFACE
 | FORM | SELECT | 0 | 15 | 0% |
 | FORM | FINISH FORM | 0 | 1 | 0% |
 | PLASTIC | SETUP | 2 | 2 | 100% |
-| PLASTIC | CREATE | 26 | 35 | 74% |
+| PLASTIC | CREATE | 27 | 35 | 77% |
 | PLASTIC | MODIFY | 18 | 32 | 56% |
 | PLASTIC | ASSEMBLE | 11 | 20 | 55% |
 | PLASTIC | CONFIGURE | 2 | 3 | 67% |
@@ -131,6 +131,7 @@ Deferred until further notice (not in the in-scope figure): MESH, FORM, SURFACE
 - SOLID › CREATE › Circular Pattern (`PatternCircular`)
 - SOLID › CREATE › Pattern on Path (`PatternOnPath`)
 - SOLID › CREATE › Mirror (`MirrorCommand`)
+- SOLID › CREATE › Thicken (`FusionSurfaceThickenCommand`)
 - SOLID › CREATE › Joint Origin (`JointOrigin`)
 - SOLID › MODIFY › Press Pull (`FusionPressPullCommand`)
 - SOLID › MODIFY › Fillet (`FusionFilletEdgesCommand`)
@@ -284,7 +285,6 @@ Deferred until further notice (not in the in-scope figure): MESH, FORM, SURFACE
 - SOLID › CREATE › Derive (`PushDeriveCommand`)
 - SOLID › CREATE › Automated Modeling (`AutomatedModelingCommand`)
 - SOLID › CREATE › Geometric Pattern (`FusionPatternGeometricCommand`)
-- SOLID › CREATE › Thicken (`FusionSurfaceThickenCommand`)
 - SOLID › CREATE › Boundary Fill (`SurfaceSculpt`)
 - SOLID › CREATE › Find Features (`FusionFindFeaturesCommand`)
 - SOLID › CREATE › Fluid Volume (`EnclosureCommand`)