fix(daemon): ship the OpenRPC document inside the crate

docs/openrpc.json lived at the repository root, outside the soulseek-rs
package, so the include_str! in proto compiled from a checkout but not
from the published tarball - cargo publish failed verification and the
v13.0.0 release stopped after publishing the lib. The document moves
into the crate's own docs/, where packaging can see it; the generator
test and every link follow.

soulseek-rs/src/daemon/proto/mod.rs

@@ -17,7 +17,7 @@ pub const PROTOCOL_VERSION: u32 = 1;
 
 /// The OpenRPC document, served by `rpc.discover` so a generator can point at
 /// a running daemon instead of needing this repository.
-pub const OPENRPC: &str = include_str!("../../../../docs/openrpc.json");
+pub const OPENRPC: &str = include_str!("../../../docs/openrpc.json");
 
 mod dto;
 mod envelope;