b5f32b7b2b
Wrapping a packed viewer in a .app or .AppImage was its own --format app value, parallel to zim and binary. But an app is really just the binary format with a bundle around it, so a separate format meant duplicating the base/icon handling and made the three formats feel like an awkward choice. Turn it into a --app flag that builds on the binary format. It composes with --base (including a webview base) and --icon, while --format stays zim or binary. The bundle builders are unchanged; only the CLI surface moves.