mount: prefer boot disk ESP and run cargo fmt

* choose ESP matching the primary data disk when multiple ESPs exist,
  falling back gracefully for single-disk layouts
* keep new helper to normalize device names and reuse the idempotent
  mount logic
* apply cargo fmt across the tree

src/report/state.rs

@@ -77,4 +77,4 @@ pub fn build_report(
 /// Write the state report JSON to disk (default path in config: /run/zosstorage/state.json).
 pub fn write_report(_report: &StateReport, _path: &str) -> Result<()> {
     todo!("serialize to JSON and persist atomically via tempfile and rename")
-}
+}