Return None from parse_number when the value overflows f64 (#3577)

Found while testing crates/doc/src/locale_number.rs:104

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

crates/doc/src/locale_number.rs

@@ -102,6 +102,9 @@ pub fn parse_number(s: &str, lang: Option<&str>) -> Option<f64> {
         return None;
     }
     let v: f64 = format!("0{int_digits}.{frac_digits}0").parse().ok()?;
+    if !v.is_finite() {
+        return None;
+    }
     Some(if neg { -v } else { v })
 }
 
@@ -151,6 +154,15 @@ mod tests {
         assert_eq!(format_number(-0.001, pl), "0,00", "a rounded zero has no sign");
     }
 
+    #[test]
+    fn overflowing_digit_strings_are_not_numbers() {
+        assert_eq!(parse_number(&"1".repeat(350), None), None);
+        assert_eq!(parse_number(&"9".repeat(400), Some("pl-PL")), None);
+        assert_eq!(parse_number(&format!("-{}", "1".repeat(350)), None), None);
+        let big = parse_number(&"1".repeat(300), None);
+        assert!(big.is_some_and(f64::is_finite), "{big:?}");
+    }
+
     #[test]
     fn cuban_and_peruvian_numbers_use_decimal_points() {
         for lang in [Some("es-CU"), Some("es-PE")] {