Blob Brush: a release away from the press point paints with Alt down

A release that arrives at a new position with no drag before it now counts
as movement, so Alt pressed at that moment no longer switches the stroke
to the Smooth tool.

crates/tools/src/draw2/gesture.rs

@@ -519,6 +519,8 @@ impl Tool for GestureTool {
                 if !self.active {
                     return vec![];
                 }
+                // A release away from the press point counts as movement.
+                self.moved |= self.points.first().is_some_and(|start| p.distance(*start) > vectorcraft_geom::EPS);
                 // Alt pressed while the pointer stood still at the press point switches the release too.
                 if self.blob_alt_smooths(ev.mods) {
                     self.smoothing = true;

crates/tools/src/draw2/gesture/tests.rs

@@ -409,6 +409,10 @@ fn blob_brush_alt_switches_to_the_smooth_tool() {
     assert_eq!(t.cursor(&cx, at, alt), Cursor::Smooth);
     let acts = t.pointer(&cx, &PointerEvent::new(PointerKind::Up, 50.0, 150.0).with_mods(alt));
     assert!(acts.is_empty(), "{acts:?}");
+    // A release away from the press point with no drag before it paints when Alt goes down.
+    t.pointer(&cx, &PointerEvent::new(PointerKind::Down, 50.0, 150.0));
+    let acts = t.pointer(&cx, &PointerEvent::new(PointerKind::Up, 150.0, 150.0).with_mods(alt));
+    assert!(matches!(acts.as_slice(), [Action::Exec(c, _)] if c == "path.blob"), "{acts:?}");
     // With nothing selected an Alt drag sends nothing.
     let none = Selection::default();
     let empty = crate::testutil::cx(&d, &none, &p);