Split Body: the face a plane split cuts takes an attachment that follows the plane (#565) (#1746)

Thanks @SychPL.

docs/action-matrix.md

@@ -257,7 +257,7 @@ resolves; it is recorded as `<action>+edit`.
 
 ## Causes
 
-Every failure, grouped by cause (5017 in all). Faces that can't take an attached sketch fail four
+Every failure, grouped by cause (5013 in all). Faces that can't take an attached sketch fail four
 actions each (`face.sketch`, `face.offset_plane`, and `face.press_pull` and `face.extrude`, which
 make a legacy face sketch there).
 
@@ -286,7 +286,6 @@ make a legacy face sketch there).
 | 9 | #568 | Construction geometry on model edges, faces and vertices is lost when a parameter moves it | `vertex.plane_three_points+edit` 5, `edge.normal_plane+edit` 2, `face.midplane+edit` 1, `face.shell+edit` 1 | 4 | demo/enclosure_steps `Enclosure/v[F2:top & F4:inner:F2:side:l4 & F4:inner:F3:blend:F2:side:l` |
 | 9 |  | Axis through a face the kernel sees as a cylinder that the command doesn't (sensor enclosure slot ends; not filed yet) | `curved.axis` 9 | 1 | examples/sensor_enclosure `Lid/F15:blend:F14:side:l2\|F14:side:l3` |
 | 7 |  | Other failures in the edit round: the hole cut and blend sizes above, and an extrude from the M0 box's top face whose profile isn't found again (not filed yet) | `face.hole+edit` 3, `face.extrude+edit` 1, `face.press_pull+edit` 1, `edge.chamfer+edit` 1 | 4 | corpus/m0-box-fillet-hole `Body1/F2:top` |
-| 4 | #565 | The face a Split Body cuts has no source (the faces it leaves whole keep theirs) | `face.offset_plane` 2, `face.sketch` 2 | 1 | oracle/22-split-body `Cyl (1)/F4:face:3` |
 | 2 |  | A helix edge projected along its axis is a point (expected) | `edge.project` 2 | 1 | oracle/50-sweep-tight-bend `Bend/F3:side:c1#1\|F3:side:c1#2~2` |
 
 Where the face history stands (`crates/kernel/src/history.rs`, [face attachments](face-attachments.md)):
@@ -297,5 +296,6 @@ chamfers, pattern and mirror copies, sides a Join merged, revolves, lofts, sweep
 shell rims, the plastic features' faces and the faces around them, and pieces of a split face (by
 the piece's own name where Offset Face moved it off the others' plane). Sheet metal panels, their
 rims and the flat ends of bends attach by name. What still refuses a sketch is what makes faces
-without recording their history (some cuts, the face a Split Body cuts): press-pull and
-extrude-from-face then fall back to a legacy face sketch found again by a point.
+without recording their history (some cuts, the face a Split Body cuts with another body's
+face): press-pull and extrude-from-face then fall back to a legacy face sketch found again by a
+point.