Phase 20.34: expand MirBuilder internal library with comprehensive lowering boxes; add pattern registry and program scanning infrastructure; implement internal lowerers for if/loop/return patterns; add dev tools and comprehensive canary tests; update VM boxes and host providers for internal delegation; wire phase2034 test suite with 30+ canary scripts covering internal lowering scenarios

Co-authored-by: factory-droid[bot] <138933559+factory-droid[bot]@users.noreply.github.com>

src/runner/modes/vm_fallback.rs

@@ -258,7 +258,22 @@ impl NyashRunner {
             }
         }
         match vm.execute_module(&module_vm) {
-            Ok(_ret) => { /* interpreter already prints via println/console in program */ }
+            Ok(ret) => {
+                use crate::box_trait::{NyashBox, IntegerBox, BoolBox};
+
+                // Extract exit code from return value
+                let exit_code = if let Some(ib) = ret.as_any().downcast_ref::<IntegerBox>() {
+                    ib.value as i32
+                } else if let Some(bb) = ret.as_any().downcast_ref::<BoolBox>() {
+                    if bb.value { 1 } else { 0 }
+                } else {
+                    // For non-integer/bool returns, default to 0 (success)
+                    0
+                };
+
+                // Exit with the return value as exit code
+                process::exit(exit_code);
+            }
             Err(e) => {
                 eprintln!("❌ VM fallback error: {}", e);
                 process::exit(1);