refactor: align platform crate boundaries

senbei-io/src/atomic.rs

@@ -0,0 +1,16 @@
+//! Shared atomic filesystem writes for native orchestration.
+
+use std::path::{Path, PathBuf};
+
+/// Write `bytes` through a sibling temporary file and replace `dest` only after
+/// the complete write succeeds.
+pub(crate) fn write_atomic(dest: &Path, bytes: &[u8]) -> std::io::Result<()> {
+    let mut temporary_name = dest.as_os_str().to_os_string();
+    temporary_name.push(".senbei-tmp");
+    let temporary = PathBuf::from(temporary_name);
+    let result = std::fs::write(&temporary, bytes).and_then(|()| std::fs::rename(&temporary, dest));
+    if result.is_err() {
+        let _ = std::fs::remove_file(&temporary);
+    }
+    result
+}