Signals read an image's alt and title text, not the title alone (#267)

xkcd's posts are an <img> whose alt and title are the comic's words. text_of dropped tags whole,
attributes and all, so Jev was sent "Feed: xkcd.com / Title: Ground Effect", ground effect being
an F1 aerodynamics term, and the comic went into the Formula 1 Signal at 0.60. With the alt text
it scores 0.19. Alt and title are read once each, and once when they say the same.

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

crates/ipx/src/signals.rs

@@ -248,21 +248,49 @@ fn chosen(answer: &serde_json::Value, candidates: &[(String, String)]) -> Option
     candidates.iter().find(|(id, _)| id == c).map(|(id, _)| id.clone())
 }
 
-/// Show notes are HTML: Jev is given their words.
+/// Show notes are HTML: Jev is given their words, and an image's alt and title text, which is all
+/// the words some posts have. xkcd's is a comic and its hover text; dropping the tag whole sent Jev
+/// "Ground Effect" alone, an F1 aerodynamics term, and the comic went into Formula 1 (#267).
 fn text_of(html: &str) -> String {
     let mut out = String::with_capacity(html.len());
-    let mut in_tag = false;
+    let mut tag: Option<String> = None;
     for c in html.chars() {
-        match c {
-            '<' => in_tag = true,
-            '>' if in_tag => { in_tag = false; out.push(' '); }
-            _ if !in_tag => out.push(c),
-            _ => {}
+        match (&mut tag, c) {
+            (None, '<') => tag = Some(String::new()),
+            (Some(t), '>') => {
+                let mut said: Vec<&str> = Vec::new();
+                for name in ["alt", "title"] {
+                    if let Some(v) = attr(t, name).filter(|v| !v.trim().is_empty() && !said.contains(v)) {
+                        said.push(v);
+                    }
+                }
+                for v in said {
+                    out.push(' ');
+                    out.push_str(v);
+                }
+                out.push(' ');
+                tag = None;
+            }
+            (Some(t), c) => t.push(c),
+            (None, c) => out.push(c),
         }
     }
     out.split_whitespace().collect::<Vec<_>>().join(" ")
 }
 
+/// A quoted attribute's value in a tag's text, `alt="..."` or `alt='...'`.
+fn attr<'a>(tag: &'a str, name: &str) -> Option<&'a str> {
+    let lower = tag.to_ascii_lowercase();
+    for q in ['"', '\''] {
+        let key = format!(" {name}={q}");
+        if let Some(at) = lower.find(&key) {
+            let rest = &tag[at + key.len()..];
+            return rest.find(q).map(|end| &rest[..end]);
+        }
+    }
+    None
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -291,6 +319,14 @@ mod tests {
         assert_eq!(chosen(&stray, &offered), None, "never one it was not offered");
     }
 
+    #[test]
+    fn an_images_words_are_read_with_the_text() {
+        let xkcd = r#"<img src="https://imgs.xkcd.com/comics/ground_effect.png" title="Runners wear sneakers." alt="Runners wear sneakers." referrerpolicy="no-referrer">"#;
+        assert_eq!(text_of(xkcd), "Runners wear sneakers.", "alt and title once, when they say the same");
+        assert_eq!(text_of("<p>Qualifying <b>report</b></p><img alt='A grid'>"), "Qualifying report A grid");
+        assert_eq!(text_of(r#"<img src="x.png" alt="">"#), "");
+    }
+
     #[test]
     fn a_batch_is_full_by_its_rows_not_its_items() {
         let item = |n: usize| Unjudged {