Every question, alert, file chooser and date picker now answers through a
callback run on the event loop instead of waiting on its thread, so the
window keeps drawing, syncing and serving the clipboard while one is open.
macOS shows them as sheets; Windows and Linux wait on them from a thread of
their own; the web build asks with dialogs on the page instead of the
browser's blocking prompts.

On Linux, where no portal, zenity or kdialog can ask, Snowbound's own
dialogs now open in the window, drawn with the interface kit, including a
file chooser, rather than as a second process, so New Notebook, Open and
Save As no longer do nothing silently on a bare desktop. Signing in to a
server whose password nothing keeps happens in Open Notebook from Server,
as on macOS, rather than in a system prompt.

Assisted-by: claude-opus-5.5