cbd-tui: show the album year, not the full release date

A notification has one line for the album, and "album (1977-10-28)"
spends it on a day nobody asked about.

`release_date` is whatever the provider's API (or fsdy's sidecar TOML)
said and is not always ISO 8601, so `release_year` reads the leading four
digits of a year-first date and returns None for anything else — an
unparseable date is dropped rather than shown raw or half-parsed, which
also keeps the "no date, no parentheses" path doing the work. `get(..4)`
is the safe form: a short string or a multi-byte boundary yields None
instead of panicking, and the tests pin both down.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

cbd-tui/src/app/now_playing.rs

@@ -630,19 +630,19 @@ fn notify_now_playing(track: &Track) {
     }
 }
 
-/// The notification body: the track, and on its own line the album with the
+/// The notification body: the track, and on its own line the album with its
-/// release date the provider gave. Most providers leave `release_date` unset
+/// release year. Most providers leave `release_date` unset (it is an optional
-/// (it is an optional proto field, so absent reads as ""), which is why the
+/// proto field, so absent reads as ""), which is why the parentheses belong to
-/// parentheses belong to the date and not to the album line — otherwise a
+/// the year and not to the album line — otherwise a dateless album shows up as
-/// dateless album shows up as "Album ()".
+/// "Album ()".
 #[cfg(feature = "notifications")]
 fn notification_body(track: &Track) -> String {
     let Some(album) = &track.album else {
         return format!("{} by {}", track.title, track.artist);
     };
-    let released = match album.release_date() {
+    let released = match release_year(album.release_date()) {
-        "" => String::new(),
+        Some(year) => format!(" ({year})"),
-        date => format!(" ({date})"),
+        None => String::new(),
     };
     format!(
         "{} by {}\n\n{}{released}",
@@ -650,6 +650,21 @@ fn notification_body(track: &Track) -> String {
     )
 }
 
+/// The year in a provider's `release_date`, for a notification that has one
+/// line to spend on the album.
+///
+/// The strings are not all ISO 8601 — each provider passes through whatever
+/// its API or (for `fsdy`) the sidecar TOML said — so this reads the leading
+/// four digits of a `YYYY`/`YYYY-MM-DD`/`YYYY/MM/DD` date and gives up on
+/// anything else rather than guessing. An unparseable date is dropped, not
+/// shown raw: it is metadata noise, and a notification is not the place to
+/// debug it.
+#[cfg(feature = "notifications")]
+fn release_year(release_date: &str) -> Option<&str> {
+    let year = release_date.trim().get(..4)?;
+    year.chars().all(|c| c.is_ascii_digit()).then_some(year)
+}
+
 /// Built without the `notifications` feature: nothing to show
 /// (architecture/build-features.md D1).
 #[cfg(not(feature = "notifications"))]
@@ -700,13 +715,15 @@ mod tests {
         notification_body(&track)
     }
 
+    /// A full date is reduced to its year; a bare year is already one.
     #[cfg(feature = "notifications")]
     #[test]
-    fn notification_shows_the_release_date_when_there_is_one() {
+    fn notification_shows_the_release_year_when_there_is_one() {
         assert_eq!(
             body_for(Some("1977-10-28")),
-            "title by artist\n\nalbum (1977-10-28)"
+            "title by artist\n\nalbum (1977)"
         );
+        assert_eq!(body_for(Some("1977")), "title by artist\n\nalbum (1977)");
     }
 
     /// No date must mean no parentheses, whether the provider left the field
@@ -718,6 +735,31 @@ mod tests {
         assert_eq!(body_for(Some("")), "title by artist\n\nalbum");
     }
 
+    /// Providers hand through whatever their API said, so a date that is not
+    /// year-first is dropped rather than shown raw or half-parsed. Nothing
+    /// here may panic — `get(..4)` has to survive a short string and a
+    /// multi-byte boundary.
+    #[cfg(feature = "notifications")]
+    #[test]
+    fn an_unparseable_release_date_is_left_out() {
+        for date in ["Oct 1977", "77", "-", "жизнь", "12/05/1977", "197"] {
+            assert_eq!(
+                body_for(Some(date)),
+                "title by artist\n\nalbum",
+                "date {date:?} should not reach the notification"
+            );
+        }
+    }
+
+    /// The year is taken from the front, whatever separator follows it.
+    #[cfg(feature = "notifications")]
+    #[test]
+    fn the_year_is_read_from_the_front_of_the_date() {
+        assert_eq!(release_year(" 1977-10-28 "), Some("1977"));
+        assert_eq!(release_year("1977/10/28"), Some("1977"));
+        assert_eq!(release_year("19771028"), Some("1977"));
+    }
+
     #[cfg(feature = "notifications")]
     #[test]
     fn notification_without_an_album_is_just_the_track() {