refactor(rule-set): reuse validated URLs during file decoding

Retain the URL parsed at entry and derive its format hint at the existing selection point instead of parsing the declaration twice. Explicit formats still require valid delivery metadata, and format precedence is unchanged.

src/rule_set/mod.rs

@@ -621,7 +621,7 @@ fn read_file(
     path: PathBuf,
     compiler: &mut Compiler,
 ) -> io::Result<Arc<Predicate>> {
-    source.parsed_url()?;
+    let url = source.parsed_url()?;
     let start = std::time::Instant::now();
     file.rewind()?;
     let metadata = file.metadata()?;
@@ -637,7 +637,8 @@ fn read_file(
     file.read_exact(prefix)?;
     file.rewind()?;
     let remote_hint = compiler.remote_files.get(&path).copied().flatten();
-    let format = source.format_with_hint(prefix, source.url_format()?.or(remote_hint))?;
+    let url_hint = url.and_then(|url| extension(Path::new(url.path())));
+    let format = source.format_with_hint(prefix, url_hint.or(remote_hint))?;
     if !matches!(
         format,
         Format::MihomoYaml | Format::MihomoText | Format::Mrs