refactor: rename aim to upm and extract appimage module

crates/upm-core/tests/metadata_zsync.rs

@@ -0,0 +1,12 @@
+use upm_core::domain::update::ParsedMetadataKind;
+use upm_core::metadata::{MetadataDocument, parse_document};
+
+#[test]
+fn parses_zsync_document_into_channel_hints() {
+    let raw = include_bytes!("fixtures/example.zsync");
+    let doc = MetadataDocument::plain_text("https://example.test/app.AppImage.zsync", raw);
+    let result = parse_document(&doc).unwrap();
+
+    assert_eq!(result.kind, ParsedMetadataKind::Zsync);
+    assert!(result.hints.primary_download.is_some());
+}