Match URL schemes case-insensitively in Url::parse and Url::join

Found while testing crates/fetch/src/http.rs:71 (Url::parse), also Url::join at :115

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

crates/fetch/src/http.rs

@@ -58,6 +58,12 @@ pub struct Url {
     pub path: String,
 }
 
+/// `s` without the leading `prefix`, matched ASCII case-insensitively (RFC 3986 §3.1).
+fn strip_scheme<'a>(s: &'a str, prefix: &str) -> Option<&'a str> {
+    let head = s.get(..prefix.len())?;
+    head.eq_ignore_ascii_case(prefix).then(|| s.get(prefix.len()..).unwrap_or_default())
+}
+
 impl Url {
     pub fn parse(s: &str) -> Result<Url, HttpError> {
         let bad = |why: &str| HttpError::BadUrl(why.to_string());
@@ -68,9 +74,9 @@ impl Url {
         if s.chars().any(|c| c.is_control() || c == ' ') {
             return Err(bad("contains spaces or control characters"));
         }
-        let (tls, rest) = if let Some(r) = s.strip_prefix("https://") {
+        let (tls, rest) = if let Some(r) = strip_scheme(s, "https://") {
             (true, r)
-        } else if let Some(r) = s.strip_prefix("http://") {
+        } else if let Some(r) = strip_scheme(s, "http://") {
             (false, r)
         } else {
             return Err(bad("only http:// and https:// are supported"));
@@ -112,7 +118,7 @@ impl Url {
     /// `Location` of a redirect, resolved against this URL.
     pub fn join(&self, location: &str) -> Result<Url, HttpError> {
         let l = location.trim();
-        if l.starts_with("http://") || l.starts_with("https://") {
+        if strip_scheme(l, "http://").is_some() || strip_scheme(l, "https://").is_some() {
             let url = Url::parse(l)?;
             if self.tls && !url.tls {
                 return Err(HttpError::BadUrl("redirect from https to http refused".into()));
@@ -618,6 +624,15 @@ mod tests {
         assert!(Url::parse("https://example.com/x?secret=abc\r\nInjected: 1").is_err());
     }
 
+    #[test]
+    fn url_scheme_is_matched_case_insensitively() {
+        let u = Url::parse("HTTPS://A.example/z").unwrap();
+        assert_eq!((u.tls, u.host.as_str(), u.port, u.path.as_str()), (true, "a.example", 443, "/z"));
+        assert!(Url::parse("Http://a.example/").is_ok());
+        let j = Url::parse("https://a.example/start").unwrap().join("HTTPS://cdn.example/file").unwrap();
+        assert_eq!((j.tls, j.host.as_str(), j.path.as_str()), (true, "cdn.example", "/file"));
+    }
+
     #[test]
     fn parses_urls() {
         let u = Url::parse("https://cdn.example.com/models/sam3/model.safetensors?sig=1#x").unwrap();