feat(daemon): wire protocol with a type-safe method vocabulary and a generated OpenRPC contract

Methods and events are enums built by one macro, so every consumer matches
exhaustively: adding a member is a compile error until the dispatcher, the
published schema, and the remote client all handle it. docs/openrpc.json is
derived from the DTOs rather than hand-written, and a test fails the build
when the checked-in copy drifts.

soulseek-rs/src/main.rs

@@ -1,6 +1,7 @@
 mod api;
 mod cli;
 mod commands;
+mod daemon;
 mod directories;
 mod models;
 mod output;