feat: Do not explicitly show delay assigned mvar

Pantograph/Serial.lean

@@ -102,7 +102,10 @@ partial def serializeExpressionSexp (expr: Expr) (sanitize: Bool := true): MetaM
     | .fvar fvarId =>
       let name := ofName fvarId.name
       pure s!"(:fv {name})"
-    | .mvar mvarId =>
+    | .mvar mvarId => do
+      if ← mvarId.isDelayedAssigned then
+        pure s!"(:mv)"
+      else
         let name := ofName mvarId.name
         pure s!"(:mv {name})"
     | .sort level =>

Test/Proofs.lean

@@ -245,7 +245,7 @@ def test_or_comm: TestM Unit := do
   let state2parent ← serializeExpressionSexp state2.parentExpr?.get! (sanitize := false)
   -- This is due to delayed assignment
   addTest $ LSpec.test "(2 parent)" (state2parent ==
-    "((:mv _uniq.43) (:fv _uniq.16) ((:c Eq.refl) ((:c Or) (:fv _uniq.10) (:fv _uniq.13)) (:fv _uniq.16)))")
+    "((:mv) (:fv _uniq.16) ((:c Eq.refl) ((:c Or) (:fv _uniq.10) (:fv _uniq.13)) (:fv _uniq.16)))")
 
   let state3_1 ← match ← state2.tryTactic (goalId := 0) (tactic := "apply Or.inr") with
     | .success state => pure state