Fix MIR builder me-call recursion and add compile tracing

src/backend/mir_interpreter/exec.rs

@@ -15,7 +15,7 @@ impl MirInterpreter {
     ) -> Result<VMValue, VMError> {
         // Safety valve: cap nested exec_function_inner depth to avoid Rust stack overflow
         // on accidental infinite recursion in MIR (e.g., self-recursive call chains).
-        const MAX_CALL_DEPTH: usize = 1024;
+        const MAX_CALL_DEPTH: usize = 128;
         self.call_depth = self.call_depth.saturating_add(1);
         if self.call_depth > MAX_CALL_DEPTH {
             eprintln!(