Fix optimizer slot clash during inlining and correct closure reduction

order

   - Add new_for_inlining to SubstitutionMap to preserve the next_slot
     counter, preventing local slot collisions when merging
     scopes.
   - Update Inliner to request fresh slots for parameters during beta
     reduction instead of forcing identity mappings.
   - Fix execution order in Optimizer::visit_node for closure inlining
     to run prepare_beta_reduction before visiting the function
     body, preventing corrupted upvalue captures.
   - Fix CLI --no-opt flag to correctly disable the optimizer in the ast
     binary.
   - Add integration test to prevent future slot clash regressions.

src/ast/compiler/optimizer/inliner.rs

@@ -128,8 +128,7 @@ impl<'a> Inliner<'a> {
                 }
 
                 if let Address::Local(slot) = addr {
-                    sub.slot_mapping.insert(*slot, *slot);
-                    sub.next_slot = sub.next_slot.max(slot.0 + 1);
+                    sub.map_slot(*slot);
                 }
                 *offset += 1;
             }