feat(fs): include full error message (#826)

.changes/fs-improve-error-message.md

@@ -0,0 +1,5 @@
+---
+"fs": patch
+---
+
+Fix promise rejection error only containing the context and stripping the actual error message.

plugins/fs/src/commands.rs

@@ -36,7 +36,11 @@ impl Serialize for CommandError {
     where
         S: Serializer,
     {
-        serializer.serialize_str(self.to_string().as_ref())
+        if let Self::Anyhow(err) = self {
+            serializer.serialize_str(format!("{err:#}").as_ref())
+        } else {
+            serializer.serialize_str(self.to_string().as_ref())
+        }
     }
 }