Incise 1.12.18

Window and tab behaviour, mostly places where Incise quietly did nothing.

• ⌘-Tab back after closing the window now shows it again. Closing the last window leaves Incise running, which is correct — but ⌘-Tab brought the app forward showing nothing, and the Dock icon was the only way back. Minimised windows are deliberately left alone, since ⌘-Tab doesn't un-minimise on macOS.
• ⌘N, File ▸ Open, and Open Folder work with the window closed. They were adding tabs to an invisible window, so the command appeared to do nothing at all.
• New document tabs open on the right, matching the terminal tabs, Safari, Finder, and Xcode. They used to appear on the left.
• Right-click a folder in the file tree ▸ Make Top Level. Go ▸ Go Up had no counterpart, so returning to the folder you came from meant going through the Open Folder panel.