refactor(device): rename from_1fs to from_one_file_system

Align with the existing naming convention used by
`Direction::from_top_down` and `BarAlignment::from_align_right`.

https://claude.ai/code/session_01LfpnUZrgq93MVZgA3KVqE6

Author: claude

src/app.rs

@@ -308,7 +308,7 @@ impl App {
                     bar_alignment: BarAlignment::from_align_right(align_right),
                     size_getter: <$size_getter as GetSizeUtils>::INSTANCE,
                     hardlinks_handler: <$size_getter as CreateHardlinksHandler<{ cfg!(unix) && $hardlinks }, $progress>>::create_hardlinks_handler(),
-                    device_boundary: DeviceBoundary::from_1fs(one_file_system),
+                    device_boundary: DeviceBoundary::from_one_file_system(one_file_system),
                     reporter: <$size_getter as CreateReporter<$progress>>::create_reporter(report_error),
                     bytes_format: <$size_getter as GetSizeUtils>::formatter(bytes_format),
                     files,

src/device.rs

@@ -8,7 +8,7 @@ pub enum DeviceBoundary {
 impl DeviceBoundary {
     /// Derive device boundary from `--one-file-system`.
     #[cfg(feature = "cli")]
-    pub(crate) fn from_1fs(one_file_system: bool) -> Self {
+    pub(crate) fn from_one_file_system(one_file_system: bool) -> Self {
         match one_file_system {
             false => DeviceBoundary::Cross,
             true => DeviceBoundary::Stay,