Function _expand_stride

Scripts/codegen/generate_ue_components.py:2532–2549

Convert mjxmacro stride expressions to plain C++ expressions usable in MjBind.h. ``MJ_M(nuser_jnt)`` -> ``m->nuser_jnt``. Fires a diagnostic if any ``MJ_*(...)`` macro survives the substitution — that's an unhandled stride shape we'd otherwise silently emit into MjBind.h verbatim.

(stride: str)

                block_label=f"subtype '{sub_key}' import block",
                diag_source="multi_uclass_inject",
            )
            c_text, _ = _inject_or_diag(
                c_text, f"SUBCLASS_{type_tag}_EXPORT", emitted.exports_cpp,
                host_path=source_path, host_kind="multi_uclass base source",
                block_label=f"subtype '{sub_key}' export block",
                diag_source="multi_uclass_inject",
            )

    # Rewrite the merged writes (drop stale base writes; replace with merged).
    writes = [w for w in writes if w.path != header_path and w.path != source_path]
    writes.append(FileWrite(path=header_path, content=h_text))
    if os.path.exists(source_path) or c_text:
        writes.append(FileWrite(path=source_path, content=c_text))
    return writes


# ---------------------------------------------------------------------------
# Pipeline: view structs
# ---------------------------------------------------------------------------

_VIEW_FIELD_TYPE_MAP = {