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

stub/tests/e2e.rs

@@ -48,11 +48,7 @@ async fn test_full_system_e2e_performance() {
     let debug_dir = manifest_dir.parent().unwrap().join("target").join("debug");
 
     let server_exe = debug_dir.join(format!("mcp-memory-server{}", std::env::consts::EXE_SUFFIX));
-    let nvim_name = if cfg!(windows) {
-        "mcp-memory-win-nvim"
-    } else {
-        "mcp-memory-linux-nvim"
-    };
+    let nvim_name = "mcp-memory-nvim";
     let nvim_exe = debug_dir.join(format!("{}{}", nvim_name, std::env::consts::EXE_SUFFIX));
     let stub_exe = debug_dir.join(format!("mcp-memory-stub{}", std::env::consts::EXE_SUFFIX));