Add a Host trait and move DB/model commands off Tauri (#558)

crates/yaak-commands/src/lib.rs

@@ -0,0 +1,23 @@
+//! Command handlers for the RPC surface, written against [`Host`] instead of
+//! any particular host.
+//!
+//! `yaak_rpc_schema` declares what each command is called and what it takes
+//! and returns; this crate is where the bodies live. Every handler has the
+//! shape the router wants — `async fn(host, Req) -> Result<Res>` — so a host
+//! registers one with a one-line adapter (or none at all), and never
+//! redeclares a command.
+//!
+//! Not every command is here yet. Handlers move in as they are freed of
+//! host-specific types; the ones that stay behind are the ones only a desktop
+//! can serve (native windows, the updater, dialogs) or that still lean on it.
+
+pub mod data;
+pub mod encryption;
+pub mod error;
+pub mod host;
+pub mod models;
+pub mod plugins;
+pub mod responses;
+
+pub use error::{Error, Result};
+pub use host::{Host, PluginHost};