[juev]

The task list and the sidebar of macOS leave clicks, selection, menus and drags to AppKit where no product decision needs our own behaviour.

What changes

• A click selects the row when the button goes down. A plain click on one of several selected rows still waits for the button to go up, because it may start a drag of all of them. Dragging an unselected row now selects it, as in Mail and Finder (R123 is updated).
• A click on the empty space of the list clears the selection, as in system tables and in Things (R44 is updated).
• Option with an arrow goes to the first or the last row; with Shift it extends the range.
• Typing the start of a title selects the task. For a second after a typed letter, Space is part of the search and ⌫ does nothing, so typing "buy milk" does not complete or delete the task it has just selected.
• A double click is the table's doubleAction.
• The context menu of a row goes through NSTableView.menu(for:), so the table outlines the row while the menu is open. ⌃click is no longer handled by hand in the table and in a subtask line.
• Several selected tasks are reordered by one drag in Inbox and in a list sorted by hand, and one undo returns them.
• The events block and the clipboard note open on a click that ends over them (click gesture recognizer instead of mouseUp).
• The sidebar draws its selection the system way while the keyboard is elsewhere (the always-emphasized row view of macOS: the task list on the system selection (SwiftUI List(selection:) or AppKit) instead of hand-made selection, clicks and menus #308 is removed).
• Esc in a popover of a card closes the card as well. In the quick entry window, where Esc throws the card away, it still closes the popover alone.

Space, ⌫ and Return of the list stay as they are (as in Things and Mail), by the decision recorded in #424.

Checks

• make apple, make apple-lint, make apple-test (new ReorderTests).
• Hidden instance of the debug build with a separate data folder: type select ("га" → "Гамма", "b" → "beta"); Space and ⌫ during typing and after a pause (three runs); reordering two selected tasks before a third and one undo.

Not checked, since they need the mouse on a visible window: selection on press, double click, the menu and its outline on right click and ⌃click (also in a subtask line), dragging several tasks between rows, the events block and the clipboard note, the look of the sidebar, Esc in a popover.

Closes #424