Phase 21.6 solidification: chain green (return/binop/loop/call); add Phase 21.7 normalization plan (methodize static boxes). Update CURRENT_TASK.md and docs.

src/backend/mir_interpreter/handlers/calls.rs

@@ -802,6 +802,30 @@ impl MirInterpreter {
         }
     }
 
+        // Fallback: user-defined function dispatch for Global calls
+        // If none of the above extern/provider/global bridges matched,
+        // try to resolve and execute a user function present in this module.
+        {
+            // Use unique-tail resolver against snapshot of self.functions
+            let fname = call_resolution::resolve_function_name(
+                func_name,
+                args.len(),
+                &self.functions,
+                self.cur_fn.as_deref(),
+            );
+            if let Some(fname) = fname {
+                if let Some(func) = self.functions.get(&fname).cloned() {
+                    // Load arguments and execute
+                    let mut argv: Vec<VMValue> = Vec::new();
+                    for a in args { argv.push(self.reg_load(*a)?); }
+                    if std::env::var("NYASH_VM_CALL_TRACE").ok().as_deref() == Some("1") {
+                        eprintln!("[vm] global-call resolved '{}' -> '{}'", func_name, fname);
+                    }
+                    return self.exec_function_inner(&func, Some(&argv));
+                }
+            }
+        }
+
     fn execute_extern_function(
         &mut self,
         extern_name: &str,