memoryd: the crate, memoryd.toml, and listening on a socket

Implemented-By: OpenCode session (model recorded in docs/implementer-log.md)

crates/memoryd/src/lib.rs

@@ -0,0 +1,4 @@
+//! The memory role: the memory files, their index, and every memory tool call (M5a spec).
+
+pub mod config;
+pub mod socket;