enum FileDialog

Native "open"/"save" file picker.

The picker is LavaExplorer, run as LavaExplorer --choose=… — the same file manager, with a bar along the bottom for the name and the answer, so Open… in any Lava app looks like the desktop it is on. It is found at LAVA_FILE_CHOOSER (a path to the binary), next to the running app's own binary (every app in this package builds into one directory), or on PATH, in that order. Without one, zenity — GTK's chooser — as before; LAVA_FILE_CHOOSER=zenity asks for it outright.

It is a subprocess either way, for the reason zenity was: a picker is a window, and a client has one surface. The chosen paths come back through a file named on the command line rather than stdout, which an app is free to fill with anything.

Blocks the calling thread until the user picks or cancels, same as any native modal dialog; call it from the main loop between frames, not from a paint closure. Returns nil on cancel, on a platform with no backend, or with no picker installed — callers should treat all three the same way ("no file chosen"), not surface them as distinct errors.