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

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

crates/memoryd/src/main.rs

@@ -0,0 +1,33 @@
+//! `memoryd serve --config <path>`.
+
+use std::ffi::OsString;
+use std::path::PathBuf;
+use std::process::ExitCode;
+
+const USAGE: &str = "usage: memoryd serve --config <path>";
+
+fn main() -> ExitCode {
+    let args: Vec<OsString> = std::env::args_os().skip(1).collect();
+    let Some(config) = parse(&args) else {
+        eprintln!("{USAGE}");
+        return ExitCode::from(2);
+    };
+    match memoryd::config::Config::load(&config) {
+        Ok(_) => {
+            eprintln!("memoryd: not implemented");
+            ExitCode::from(2)
+        }
+        Err(e) => {
+            eprintln!("memoryd: {e}\nsee docs/runbook.md#memoryd-start-failed");
+            ExitCode::from(1)
+        }
+    }
+}
+
+/// The config path of `serve --config <path>`, or `None` for any other list.
+fn parse(args: &[OsString]) -> Option<PathBuf> {
+    match args {
+        [serve, flag, path] if serve == "serve" && flag == "--config" => Some(PathBuf::from(path)),
+        _ => None,
+    }
+}