3D and Materials: Inflate takes Twist, Taper and Cap

The public 3D and Materials panel options list Depth, Twist, Taper and Cap
for every 3D type; Inflate had only Depth.

- Twist (0° to 360°) and Taper (1–100 %) turn and scale the back about the
  shape's centre, as Extrude & Bevel's do: a puffed back is turned and
  lowered in proportion, and the sides follow in slices.
- Cap: Solid closes the back; Hollow leaves it off, so the inflated front is
  a shell open behind. The documentation doesn't say what Cap means for
  Inflate; this reading is stated in docs/three-d.md.
- The dialog's Object tab shows them in the documented order (Depth, Twist,
  Taper, Cap), then Volume and Both sides.

At 0 % volume a twisted, tapered Inflate has the extrusion's outline from
every side (tested).

A twisted, tapered, hollow Inflate draws on the canvas exactly as it
exports, and expands to faces with their own ids (tested). ROADMAP and the
parity pages list the new options; the 3D score stays at ~25 %.

crates/render/src/tests_objectfx.rs

@@ -65,13 +65,15 @@ fn revolve_canvas_matches_baked_art_and_shades_its_surface() {
     assert_eq!(live.pixels, render_threads(&d, 4).pixels);
 }
 
-/// Extrude & Bevel, Inflate and Rotate draw on the canvas exactly as they export, filling more
-/// than the flat square with faces of differing shades (Rotate: one shade, narrower).
+/// Extrude & Bevel, Inflate (also twisted, tapered and hollow) and Rotate draw on the canvas exactly
+/// as they export, filling more than the flat square with faces of differing shades (Rotate: one
+/// shade, narrower).
 #[test]
 fn solid_effects_canvas_matches_baked_art_and_shades_their_faces() {
     for (effect, params) in [
         ("threeD.extrude", json!({"depth": 30, "bevel": "rounded"})),
         ("threeD.inflate", json!({"depth": 10})),
+        ("threeD.inflate", json!({"depth": 10, "twist": 90, "taper": 60, "cap": false, "rotationX": -20, "rotationY": 35})),
         ("threeD.rotate", json!({"rotationX": 0, "rotationY": 55, "rotationZ": 0})),
     ] {
         let mut n = Node::path(