The browser has no file system a page can call synchronously. On wasm32,
fieldcraft_io::fs now reads and writes files kept in memory (memory.rs,
after SolidCraft's vfs): the web host puts picked and dropped files in
and takes out what commands wrote. The recovery folder works over the
same calls (list, remove, is_file), with in-memory entry locks and a
host-provided clock on wasm, so autosave and File > Recover work in the
browser as on the desktop. Native behaviour is unchanged.
Part of #119
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm
