v0.25.0: Ask AI, account-wide file history, disk saves always sync

• Disk saves always sync. The editor and desktop app now notice every file from disk changing, not only the open one, so a file saved in another editor reaches the account. Large stored files are checked by size and time (desktop 0.18.0 adds a stat call for that). (#64)
• File history on the account. Each synced change is kept as an end-to-end encrypted version (50 per file). History lists versions from every device, with Restore. Shared documents: viewers see the history, editors can restore. (#64)
• Ask AI at readm3.com/talk: talk to a file, a folder or the workspace, 10 free questions a day. (#63)