- file.save / file.saveAs / file.saveACopy add the .designcraft extension to a
given path that lacks it and report the path written; saving back to the
document's own file keeps its name.
- file.open tells DesignCraft and IDML packages apart by content, so files
without an extension open; anything else is "not a DesignCraft or IDML file".
- Dropped or web-picked files without an extension open as documents when their
content is one.
- Desktop save dialogs filter on the suggested extension and add it to a name
typed without it, asking before replacing an existing file; the open dialog
gains "All files".
- macOS: open-documents Apple events (Finder, Dock, Open With) through
fmv-macos-events, queued until the window is ready; Info.plist declares the
.designcraft type and an imported .idml type with CFBundleDocumentTypes.
- Windows MSI: .designcraft ProgId with an Open verb, IDML under Open with.
- Linux: shared-mime-info for both types and MimeType in the .desktop file.
Fixes#158, #211, #375
aiongg