Linux app id: ai.storyteller.solidcraft, with an end-of-life rebase from the old id (#619)

The Flatpak app id, desktop/metainfo/MIME file names, icon name and the window's Wayland app_id / X11 class are now ai.storyteller.solidcraft, the id the ArtCraft launcher expects.

Existing Flatpak installs move over: the Pages repo marks app/ai.storyteller.solvecraft end-of-life with a rebase to the new id, so flatpak update offers the switch and Flatpak carries ~/.var/app along. A new install next to the old one copies settings and autosaves on first launch through a read-only grant on the old data folder. The metainfo declares <replaces>/<provides>, the desktop entry X-Flatpak-RenamedFrom, and AppImages drop the menu entry an older AppImage installed. deb/rpm upgrades remove the old-named files.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/io/src/lib.rs

@@ -23,7 +23,7 @@ mod threemf;
 pub mod vfs;
 
 pub use dxf::{read_dxf, write_dxf};
-pub use legacy_dir::adopt_legacy_dir;
+pub use legacy_dir::{APP_ID, LEGACY_APP_ID, adopt_legacy_dir, legacy_flatpak_path};
 pub use safe_write::{backup_path, write_atomic};
 pub use sketch2d::{Geom2, MAX_DRAWING_BYTES};
 pub use svg::read_svg;