refactor: consolidate nvim crates, extract server library, and update workspace dependencies

mcp-memory-nvim/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "mcp-memory-nvim"
+version = "1.0.0"
+edition = "2024"
+
+[dependencies]
+serde_json = "1.0"
+tokio = { version = "1.37", features = ["full"] }
+
+nvim-core = { path = "../nvim-core" }