chore: convert to cargo workspace with four crates

crates/xy-ipc/Cargo.toml

@@ -0,0 +1,16 @@
+[package]
+name = "xy-ipc"
+edition.workspace = true
+version.workspace = true
+license.workspace = true
+
+[dependencies]
+xy-protocol.workspace = true
+tokio.workspace = true
+serde.workspace = true
+serde_json.workspace = true
+tracing.workspace = true
+thiserror.workspace = true
+
+[dev-dependencies]
+tempfile.workspace = true

crates/xy-ipc/src/lib.rs

@@ -0,0 +1 @@
+//! JSON-RPC 2.0 over newline-delimited JSON on a Unix socket.