Image sets by their numbered name, digits kept

Without a file counter a subject-named image release was bounded by the
image's name with all numbers removed:
- STIRILING SILVER's sets stp250x…stp465x became one 44k-image release
  (all "stp x"); picture threads of many sets (keira_s04, keira_s05,
  perla_s01, apneatic-7, -8 …) one release each.
- Free-text names without numbers ("JimAndJoey Kindly Husband-to-Be.JPG")
  made each image a set: one thread was 1,177 releases.
The bound is now the name up to its last number with its digits
("stp250x", "keira_s05_l keira_s05_", "apneatic-7-"), and nothing for a
name without numbers. models fixture: 172 -> 754 releases, by set. Both
implementations; tests; fixtures identical.

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

edge/src/names.rs

@@ -414,6 +414,18 @@ static AUDIO: LazyLock<Regex> = LazyLock::new(|| re(r"(?i)\.(mp3|flac|m4a|m4b|og
 static DOCUMENT: LazyLock<Regex> = LazyLock::new(|| re(r"(?i)\.(pdf|epub|mobi|azw3?|djvu|cbr|cbz|cb7|chm|lit|docx?)$"));
 
 /// An image set's name without a counter: up to the last number, without numbers.
+/// `/\d/.test(stem) ? stem.replace(/\d+\D*$/, '') : ''`: an image's set, digits kept.
+fn image_set(stem: &str) -> String {
+    let b = stem.as_bytes();
+    match b.iter().rposition(u8::is_ascii_digit) {
+        Some(last) => {
+            let start = b[..=last].iter().rposition(|c| !c.is_ascii_digit()).map_or(0, |i| i + 1);
+            stem[..start].to_string()
+        }
+        None => String::new(),
+    }
+}
+
 fn image_prefix(stem: &str) -> String {
     let b = stem.as_bytes();
     let cut = match b.iter().rposition(u8::is_ascii_digit) {
@@ -599,7 +611,8 @@ pub fn release_identity(poster: &str, subject: &str, name: &str) -> Release {
     // An image set's subject may be one word, the model's name: /^[A-Za-z]{3,}$/.
     let one_word = image && remainder.len() >= 3 && remainder.bytes().all(|c| c.is_ascii_alphabetic());
     if !tag && (names_release(&remainder) || one_word) {
-        let bound = counter_total(subject).unwrap_or_else(|| prefix.clone());
+        // Without a counter an image's set: its name up to its last number, digits kept; none without numbers.
+        let bound = counter_total(subject).unwrap_or_else(|| if image { image_set(&stem) } else { String::new() });
         return Release { key: hash(&["subject", poster, &remainder, &bound]), name: remainder, source: "subject", file_total };
     }
     if let Some(total) = post_total.filter(|&n| n != 0 && !tag) {
@@ -1117,6 +1130,15 @@ mod image_set_tests {
         assert!(!random_poster("w.merklein@freenet.de (muffin)"));
     }
 
+    #[test]
+    fn image_sets_by_their_numbered_name() {
+        let silver = |n: &str| release_identity("p", &format!(r#"The excellent STIRILING SILVER - Always popular - "{n}" yEnc 320794 bytes"#), n);
+        assert_eq!(silver("stp250x001.jpg").key, silver("stp250x002.jpg").key);
+        assert_ne!(silver("stp250x001.jpg").key, silver("stp305x001.jpg").key);
+        let mint = |n: &str| release_identity("Cert", &format!(r#"I'm not a breath mint, but I am not all there either. [{n}" yEnc]"#), n);
+        assert_eq!(mint("JimAndJoey Kindly Husband-to-Be.JPG").key, mint("Oops OnlyOneMore.JPG").key);
+    }
+
     #[test]
     fn dates_are_no_counters() {
         use super::counter_total;