fix(lib): keep a missing download directory as the target, not its parent

resolve_download_path treated "not a directory" as "names a file" and
fell back to the parent, so a directory that simply did not exist yet
redirected the transfer one level up. The CLI and TUI create the folder
before downloading and never hit it; a daemon does not, so its transfers
landed in ~/Downloads while daemon.status - and the paths download and
get report - named ~/Downloads/Soulseek. Green on any machine where the
folder already exists, which is how it survived to CI.

Only an existing file diverts to the parent now. PartFile::open already
creates the directory it streams into.

soulseek-rs-lib/src/peer/download_peer.rs

@@ -75,10 +75,15 @@ fn extract_filename_from_path(full_path: &str) -> &str {
 
 /// Where a download's bytes end up: its configured directory (falling back
 /// to the parent if it names a file) joined with the remote basename.
+///
+/// A directory that does not exist yet stays the target — `PartFile::open`
+/// creates it. Treating it as "not a directory" and dodging to the parent
+/// made a daemon whose folder was never created download into `~/Downloads`
+/// while reporting `~/Downloads/Soulseek`.
 fn resolve_download_path(download: &Download) -> Result<String, DownloadError> {
     let mut expanded_path = expand_tilde(&download.download_directory);
 
-    if !expanded_path.is_dir() {
+    if expanded_path.is_file() {
         expanded_path = expanded_path
             .parent()
             .ok_or_else(|| {
@@ -527,6 +532,23 @@ mod tests {
         }
     }
 
+    #[test]
+    fn a_directory_that_does_not_exist_yet_is_created_not_dodged() {
+        let dir = scratch_dir("fresh").join("Soulseek");
+
+        let mut part = PartFile::open(&download_into(&dir, 4)).unwrap();
+        part.write(b"data").unwrap();
+        let final_path = part.finish().unwrap();
+
+        assert_eq!(
+            std::path::Path::new(&final_path).parent(),
+            Some(dir.as_path()),
+            "the bytes belong in the configured directory, not its parent"
+        );
+        assert_eq!(std::fs::read(&final_path).unwrap(), b"data");
+        let _ = std::fs::remove_dir_all(dir.parent().unwrap());
+    }
+
     #[test]
     fn a_partial_file_sets_the_resume_offset() {
         let dir = scratch_dir("resume");