Move vmlinuz out of registry dir.

src/registry.rs

@@ -26,6 +26,12 @@ pub(crate) fn validate_image_name(name: &str) -> Result<()> {
     Ok(())
 }
 
+pub(crate) fn vmlinuz_path() -> Result<PathBuf> {
+    let base = xdg::BaseDirectories::with_prefix("boco");
+    base.place_data_file("vmlinuz")
+        .context("Failed to create XDG_DATA_HOME subdirectory")
+}
+
 pub(crate) fn registry_base_dir() -> Result<PathBuf> {
     let base = xdg::BaseDirectories::with_prefix("boco");
     base.create_data_directory("registry")