fix(tvix/eval): context-aware… hasContext

Yes, `hasContext e` should work where `e` is a contextful strings, otherwise, it is really useless.

Change-Id: I5eb071fc257217d6e8a63fe519132ebd98186696
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10617
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>

tvix/eval/src/builtins/mod.rs

@@ -680,7 +680,7 @@ mod pure_builtins {
             return Ok(e);
         }
 
-        let v = e.to_str()?;
+        let v = e.to_contextful_str()?;
         Ok(Value::Bool(v.has_context()))
     }