Holes on round faces from the app, and Flip for holes at sketch points (#980)

* Holes on round faces from the app, one hole per pick, and Flip for holes at sketch points (#967)

The Hole dialog takes any face: a hole on a round face drills against the face's normal where it
was picked, and its arrow shows that. A round face split at its seam is picked whole, but makes
one hole where it was clicked. Holes at sketch points get Flip (saved as flip in the hole's points,
under format 18), in the command and in the dialog.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Holes at sketch points show their arrow: into the part, or away with Flip (#967)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

crates/doc/src/format.rs

@@ -129,6 +129,9 @@
 //!   taken from another face whose plane passed near the point, such as the far side of a thin
 //!   plate or a face of another body at the same height) is mirrored into that face when the
 //!   design is evaluated. Holes whose direction enters their face build as before.
+//!   Holes at sketch points can be flipped (`flip: true` in the hole's `points`): they drill away
+//!   from the side they would go into by themselves. Holes without it save as before; 0.9.0 would
+//!   drop the flip and drill the other way.
 
 //! - 19: editable associative offset-distance dimensions. Older offsets retain their saved
 //!   fixed distances; migration does not invent dimensions or change geometry.