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/Cargo.toml

@@ -44,4 +44,5 @@ keyring = { version = "3", features = ["apple-native", "windows-native", "async-
 chrono = { version = "0.4.45", default-features = false, features = ["clock", "serde"] }
 
 [dev-dependencies]
+schemars = "1.2.1"
 tempfile = "3"