Fix stopping a panel b/w anchors after an interruption

The panel(surface view) could stop b/w anchors if the pan gesture doesn't
pass through `.changed` state after an interruptible animator is interrupted.

The possible reason is the constraints have never changed since the last animation
is committed so that `surfaceView.superview!.layoutIfNeeded()` doesn't trigger
a layout update by the constraint-based layout system in
`FloatingPanelLayoutAdapter.activateLayout(of:)`.

Thus the inserted code changes a panel interactive constraint by the least
positive number. It allows the constraint-based layout system to update the
surface layout expectedly.

Framework/Sources/FloatingPanel.swift

@@ -344,7 +344,7 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate {
 
             if let animator = self.animator {
                 guard surfaceView.presentationFrame.minY >= layoutAdapter.topMaxY else { return }
-                log.debug("panel animation interrupted!!!")
+                log.debug("panel animation(interruptible: \(animator.isInterruptible)) interrupted!!!")
                 if animator.isInterruptible {
                     animator.stopAnimation(false)
                     // A user can stop a panel at the nearest Y of a target position so this fine-tunes
@@ -377,6 +377,12 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate {
             case .ended, .cancelled, .failed:
                 if interactionInProgress == false {
                     startInteraction(with: translation, at: location)
+                    // Workaround: Prevent stopping the surface view b/w anchors if the pan gesture
+                    // doesn't pass through .changed state after an interruptible animator is interrupted.
+                    let dy = translation.y - .leastNonzeroMagnitude
+                    layoutAdapter.updateInteractiveTopConstraint(diff: dy,
+                                                                 allowsTopBuffer: true,
+                                                                 with: behavior)
                 }
                 panningEnd(with: translation, velocity: velocity)
             default:

Framework/Sources/FloatingPanelLayout.swift

@@ -454,6 +454,7 @@ class FloatingPanelLayoutAdapter {
     func activateLayout(of state: FloatingPanelPosition) {
         defer {
             surfaceView.superview!.layoutIfNeeded()
+            log.debug("activateLayout -- surface.presentation = \(self.surfaceView.presentationFrame) surface.frame = \(self.surfaceView.frame)")
         }
 
         var state = state