fix: accept existing handles with trailing underscores

src/config.rs

@@ -563,14 +563,13 @@ pub(crate) fn normalize_channel(input: &str) -> io::Result<String> {
         .or_else(|| input.strip_prefix("https://youtube.com/"));
     let address = url_address.unwrap_or(input);
     if let Some(handle) = address.strip_prefix('@') {
+        // Validate address safety, not creation rules: existing handles can have edge separators.
         let length = handle.chars().count();
         if length == 0
             || length > 30
             || !handle
                 .chars()
                 .all(|c| c.is_alphanumeric() || matches!(c, '_' | '-' | '.'))
-            || !handle.starts_with(char::is_alphanumeric)
-            || !handle.ends_with(char::is_alphanumeric)
         {
             return Err(invalid("Invalid YouTube channel handle"));
         }
@@ -787,6 +786,34 @@ mod tests {
         }
     }
 
+    #[test]
+    fn existing_edge_separator_handles_can_be_saved_and_reloaded() {
+        let channel = "https://www.youtube.com/channel/UC4QobU6STFB0P71PMvOGN5A";
+        for handle in ["@hontame_", "@_creator", "@.creator-"] {
+            let directory = TestDirectory::new();
+            let path = directory.0.join("config.toml");
+            let tags = BTreeMap::from([("Immersion".to_owned(), true)]);
+            let saved = set_channel_tags(&path, &tags, handle, channel).unwrap();
+            assert_eq!(saved.channels[handle], channel);
+            assert_eq!(saved.categories["Immersion"], [channel]);
+            let reloaded = load(&path).unwrap();
+            assert_eq!(reloaded.channels, saved.channels);
+            assert_eq!(reloaded.categories, saved.categories);
+            let unchecked = BTreeMap::from([("Immersion".to_owned(), false)]);
+            set_channel_tags(
+                &path,
+                &unchecked,
+                &format!("https://www.youtube.com/{handle}"),
+                channel,
+            )
+            .unwrap();
+            let reloaded = load(&path).unwrap();
+            assert!(reloaded.categories["Immersion"].is_empty());
+            assert_eq!(reloaded.channels[handle], channel);
+            assert_eq!(reloaded.channels.len(), 1);
+        }
+    }
+
     #[test]
     fn key_remaps_survive_all_saves_and_section_orders() {
         use crate::keys::{Action, Context};