Report a missed first 2Points pick at once for Horizontal/Vertical

The first empty-space click of the 2Points flow was only resolved against
the document together with the second one, so "No valid constraint point
found." appeared one pick late. The command now hands the first pick to
the host (`CmdResult::CheckHorizontalPoint`), which resolves it right away:
a miss reports and re-asks for the first point, a hit moves on to the
second point.

Co-Authored-By: Claude Fable 5.1 <[email protected]>

src/modules/parametric/horizontal.rs

@@ -321,10 +321,12 @@ impl CadCommand for HorizontalConstraintCommand {
     fn on_point(&mut self, point: DVec3) -> CmdResult {
         let pick = Self::point_pick(None, point);
         match self.step {
-            Step::ObjectOrTwoPoints | Step::FirstPoint => {
-                self.step = Step::SecondPoint(pick);
-                CmdResult::NeedPoint
-            }
+            // The host resolves the pick against the document: a hit resumes
+            // at the second point, a miss re-asks for the first one at once.
+            Step::ObjectOrTwoPoints | Step::FirstPoint => CmdResult::CheckHorizontalPoint {
+                kind: self.kind,
+                pick,
+            },
             Step::SecondPoint(first) => self.finish_points(first, pick),
         }
     }
@@ -375,10 +377,12 @@ mod tests {
     fn enter_starts_the_two_point_flow() {
         let mut command = HorizontalConstraintCommand::new();
         assert!(matches!(command.on_enter(), CmdResult::NeedPoint));
-        assert!(matches!(
-            command.on_point(DVec3::new(1.0, 2.0, 0.0)),
-            CmdResult::NeedPoint
-        ));
+        let CmdResult::CheckHorizontalPoint { kind, pick } =
+            command.on_point(DVec3::new(1.0, 2.0, 0.0))
+        else {
+            panic!("the host must check the first point");
+        };
+        let mut command = HorizontalConstraintCommand::resume(kind, Some(pick));
         let CmdResult::AddHorizontalConstraint {
             selection: HorizontalConstraintSelection::Points(first, second),
             direction,