Ghost FTP 0.99.28 — Windows/Linux desktop reliability (Preview candidate)

Previous published canonical release: v0.99.27.

User-facing fixes

• Windows/Linux Folder Sync: a configured on-demand virtual folder can no longer silently appear enabled when the current OS/build cannot support it. The backend rejects unsupported creation and re-enabling before SQLite persistence, shows an error for previously imported active records and avoids registering fake virtual roots. Mirrored sync is unaffected.
• Linux saved credentials: vault helper commands used for lookup, storing and deleting OS-protected credentials now use a bounded 30-second wait and process cleanup on deadline. The UI receives a clear failure when the desktop keyring is stalled instead of hanging indefinitely. No plaintext credentials, new service or hidden fallback.
• Tests: Rust regression tests for VirtualFs capability gating, and Linux Secret Service subprocess timeout, cleanup and exact byte preservation. The existing Windows/Linux, Rust and FTP/FTPS/SFTP matrix remains mandatory.

Scope and limitations

This is a desktop reliability Preview, not a certification that all Windows/Linux features are complete. Real signed Windows upgrades, Linux distribution-specific installers/portals/keyrings, actual on-demand Cloud Filter hydration, all cloud-vendor authorization flows, large and interrupted transfers, accessibility and device-specific pixel parity still require controlled end-to-end acceptance. Android and macOS receive only the synchronized version metadata; no platform features are implied by that bump.

The release must not be merged or published until all required exact-head CI gates are successful. Do not rewrite the existing v0.99.27 assets.