test(mvn): tighten verify savings threshold to 90%

Actual savings on the trimmed fixture are 97%+. The 60% floor left a
large regression window — bump to 90% so meaningful degradation fails
the test while still giving headroom.

Author: mariuszs

src/cmds/java/mvn_cmd.rs

@@ -1855,8 +1855,8 @@ mod tests {
         let savings = 100.0 - (output_tokens as f64 / input_tokens as f64 * 100.0);
 
         assert!(
-            savings >= 60.0,
-            "mvn verify auth: expected >=60% savings, got {:.1}% ({} -> {} tokens)",
+            savings >= 90.0,
+            "mvn verify auth: expected >=90% savings, got {:.1}% ({} -> {} tokens)",
             savings,
             input_tokens,
             output_tokens,