A listed feed nobody subscribes to downloads nothing (#107)

With no subscribers a feed falls back to its own settings, where auto_download is on, so a
listed feed with audio would have downloaded files for no one. The seeded news feeds carry
only images, which media_types already skips, so nothing was downloaded. Files skipped for it
are judged again, by the new subscriber's settings, on the next scan after someone subscribes.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/main.rs

@@ -1725,7 +1725,10 @@ fn merge_policy(subs: &[db::Sub], feed_cfg: &config::Feed, global: usize) -> Pol
 
     if subs.is_empty() {
         return Policy {
-            auto_download: feed_cfg.auto_download,
+            // A feed listed in the Directory with nobody subscribed is there to be found, not
+            // downloaded: its files would be for no one. Once someone subscribes, the files
+            // skipped for it are judged again on the next scan, by their settings (#107).
+            auto_download: feed_cfg.auto_download && !feed_cfg.listed,
             allow_explicit: feed_cfg.allow_explicit,
             wants: vec![Want { keywords: feed_cfg.keywords.clone(), blocked: vec![] }],
             budget: cap(feed_cfg.max_new_per_check),
@@ -1958,6 +1961,14 @@ fn duration(secs: u64) -> String {
 mod tests {
     use super::*;
 
+    #[test]
+    fn a_listed_feed_nobody_subscribes_to_downloads_nothing() {
+        let mut f = feed();
+        assert!(merge_policy(&[], &f, 3).auto_download);
+        f.listed = true;
+        assert!(!merge_policy(&[], &f, 3).auto_download);
+    }
+
     #[test]
     fn a_failing_feed_backs_off_doubling_up_to_a_day() {
         let hour = 3600;