fix: a hole at sketch points drills into the part its sketch touches (#910)

Hole centres from a sketch now drill into the material on whichever side of the sketch plane it lies: material the spot starts in wins, then the nearest body ahead, else against the sketch normal as before. A sketch on a part's underside or below it now drills up into the part. Covers counterbores, through-all, edge and corner centres, patterns and reopening.

crates/engine/src/cmd/features.rs

@@ -51,7 +51,7 @@ pub static COMMANDS: &[CommandSpec] = &[
         .at("SOLID", "CREATE")
         .icon("hole")
         .key("H")
-        .params("position: [x,y,z] on a face | sketch + points: [sketch point ids] (one hole each, perpendicular to the sketch) | sketch alone (every sketch point: standalone points and circle centres); direction?: [x,y,z] (default: into the face); diameter | thread (a tapped hole: the tap drill, major − pitch) | clearance: \"M6\" with fit?: close|normal|loose (ISO 273); depth? (default through all) | to?: [x,y,z] (To Object: drill to that face or point); type?: simple|drilled|counterbore|countersink; tip_angle?; cb_diameter?, cb_depth?; cs_diameter?, cs_angle?; thread?: \"M6\" (cosmetic)"),
+        .params("position: [x,y,z] on a face | sketch + points: [sketch point ids] (one hole each, perpendicular to the sketch, into the material on whichever side of the sketch plane it is) | sketch alone (every sketch point: standalone points and circle centres); direction?: [x,y,z] (default: into the face; ignored with sketch points); diameter | thread (a tapped hole: the tap drill, major − pitch) | clearance: \"M6\" with fit?: close|normal|loose (ISO 273); depth? (default through all) | to?: [x,y,z] (To Object: drill to that face or point); type?: simple|drilled|counterbore|countersink; tip_angle?; cb_diameter?, cb_depth?; cs_diameter?, cs_angle?; thread?: \"M6\" (cosmetic)"),
     CommandSpec::new("solid.pipe", "Pipe", pipe)
         .at("SOLID", "CREATE")
         .icon("pipe")