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/substitution_map.rs

@@ -38,6 +38,12 @@ impl SubstitutionMap {
         inner
     }
 
+    pub fn new_for_inlining(&self) -> Self {
+        let mut inner = self.new_inner();
+        inner.next_slot = self.next_slot;
+        inner
+    }
+
     pub fn add_ast_substitution(&mut self, addr: Address, node: AnalyzedNode) {
         self.ast_substitutions.insert(addr, Rc::new(node));
     }