feat: bootstrap awg2 harness rust workspace and docs

traffic_core/src/lock.rs

@@ -0,0 +1,28 @@
+use std::{fs, path::Path};
+
+pub struct FileLock {
+    path: String,
+}
+
+impl FileLock {
+    pub fn acquire(path: &str) -> anyhow::Result<Self> {
+        let p = Path::new(path);
+        if let Some(parent) = p.parent() {
+            fs::create_dir_all(parent)?;
+        }
+        if p.exists() {
+            anyhow::bail!("lock already exists: {path}");
+        }
+        fs::write(p, std::process::id().to_string())?;
+        Ok(Self {
+            path: path.to_string(),
+        })
+    }
+}
+
+impl Drop for FileLock {
+    fn drop(&mut self) {
+        let _ = fs::remove_file(&self.path);
+    }
+}
+