feat: enhance duplicate code diagnostic message

Include the count of duplicate locations in the diagnostic message for better
clarity. This helps developers quickly understand how many instances of
duplicated code exist without having to expand the details.

Author: yingmanwumen

crates/echolysis-lsp/src/server/diagnostic.rs

@@ -22,7 +22,10 @@ impl Server {
         location: &lsp_types::Location,
         other_locations: &[lsp_types::Location],
     ) -> lsp_types::Diagnostic {
-        let message = "Duplicated code fragments found\n".to_string();
+        let message = format!(
+            "Duplicated code fragments found in {} place(s)",
+            other_locations.len()
+        );
         lsp_types::Diagnostic {
             range: location.range,
             severity: Some(lsp_types::DiagnosticSeverity::INFORMATION),