Fixes#1756
We previously converted from view to screen coordinates but if the view
doesn't take up the full window then the view coordinates are wrong. We
need to convert to window coordinates in the middle.
Previously files would be pasted as only the filename. This commit
introduces an extension to NSPasteboard which provides a method to
consistently get the string contents of a pasteboard so that the
behavior can stay the same anywhere where we need to do that.
Fixes#1500
This overhauls how we do focus management for surfaces to make it more
robust. This DID somehow all work before but was always brittle and was
a sketchy play with SwiftUI/AppKit behavior across macOS versions.
The new approach uses our window controller and terminal delegate
system to disseminate focus information whenever any surface changes
focus. This ensures that only ONE surface ever has focus in libghostty
because the controller ensures it is widely distributed.
