style(eql-mapper): simplify unused variable binding in EXPLAIN handler

Move comment and underscore prefix into pattern destructuring rather
than using a separate let binding to suppress the unused variable warning.

Author: tobyhede

packages/eql-mapper/src/inference/infer_type_impls/statement.rs

@@ -80,16 +80,14 @@ impl<'ast> InferType<'ast, Statement> for TypeInferencer<'ast> {
             }
 
             Statement::Explain {
-                statement: inner_statement,
+                // Note: inner statement's type inference happens through normal AST traversal
+                statement: _inner_statement,
                 ..
             } => {
                 // Recursively type-check the inner statement so transformations apply
                 // EXPLAIN itself returns metadata, not the query results - give it empty projection
                 self.unify_node_with_type(statement, Type::empty_projection())?;
-                // Note: inner statement's type inference happens through normal AST traversal
-                let _inner_statement = inner_statement; // Handled by visitor
             }
-
             _ => {}
         };