mac/dialog: release all input keys when modal steals key input

modal dialogs steal the key/mouse input and possibly eat corresponding
key up events when opening via key binding. this leads to key sequence
ends to not reported and key bindings not being triggered if no key up
event was triggered after closing the modal.

osdep/mac/dialog.swift

@@ -18,7 +18,7 @@
 import Cocoa
 import UniformTypeIdentifiers
 
-class Dialog {
+class Dialog: NSObject, NSWindowDelegate, NSOpenSavePanelDelegate {
     var option: OptionHelper?
 
     init(_ option: OptionHelper? = nil) {
@@ -48,6 +48,7 @@ class Dialog {
         panel.canChooseDirectories = directories
         panel.allowsMultipleSelection = multiple
         panel.allowedContentTypes = types
+        panel.delegate = self
 
         if panel.runModal() == .OK {
             return panel.urls.map { $0.path }
@@ -83,4 +84,8 @@ class Dialog {
         alert.addButton(withTitle: "Ok")
         alert.runModal()
     }
+
+    func windowDidBecomeKey(_ notification: Notification) {
+        AppHub.shared.input.put(key: MP_INPUT_RELEASE_ALL)
+    }
 }