Some echo()/print() fixes. (0.37.12)

src/vm/echo.c

@@ -1,12 +1,22 @@
 /**
  * Implements OP_ECHO: print top-of-stack value without trailing newline.
- * Does not store into VM output buffer; writes directly to stdout and flushes.
+ * Now stores the value into the VM's output buffer and marks it as partial,
+ * so the CLI can render echo output together with following print output.
  */
 
 case OP_ECHO: {
     Value v = pop_value(vm);
-    print_value(&v);
-    fflush(stdout);
+    Value snap = deep_copy_value(&v);
     free_value(v);
+    if (vm->output_count < OUTPUT_SIZE) {
+        int idx = vm->output_count;
+        vm->output[idx] = snap;
+        vm->output_is_partial[idx] = 1; // ECHO does not end the line
+        vm->output_count++;
+    } else {
+        free_value(snap);
+        fprintf(stderr, "Runtime error: output buffer overflow\n");
+        exit(1);
+    }
     break;
 }