score/utils: Update component and feature architecture to match current code base

The component requirement IDs for `score/utils` were reworked in #475 and `comp_req__utils__scoped_operation` is being moved out of Utils and into `score/scope_exit` via #428. Neither of these changes updates the Utils component architecture, so it still describes a codebase state that no longer matches reality.

`utils/docs/architecture/index.rst` still has the `comp__baselibs_utils` component `:implements:` `logic_arc_int__baselibs__utils_scoped_op`, the `comp_arc_sta__baselibs__utils` node still `:fulfils:` the old `comp_req__utils__base64`/`comp_req__utils__scoped_operation` IDs, and the scoped-op constructor/destructor interface operations are still defined there even though that functionality does not belong to Utils. There is also no architecture element for the Meyer singleton (`score/utils/meyer_singleton/`) or `static_destruction_guard.h`, which are part of the current Utils code but have no architectural representation at all.

`docs/features/architecture/index.rst` also references `logic_arc_int__baselibs__utils_scoped_op` and `logic_arc_int__baselibs__utils_base64`, so the feature architecture needs the corresponding adjustments once the component architecture is fixed.

This should be addressed once #428 has landed, so the Utils architecture can be updated to drop the scoped-operation interface, rename the base64 interface elements to match the current requirement IDs, and add the missing Meyer singleton architecture element.

Follow-up from review comment on #417.

After #428 lands, compare the current Utils code and requirement IDs with utils/docs/architecture/index.rst. Update the Utils component architecture, including the scoped-operation removal, Base64 identifiers, Meyer singleton, and static_destruction_guard.h, then adjust docs/features/architecture/index.rst to remove stale references. Done means both architecture files describe the current code without obsolete IDs.

Written by the indexing model from the issue text.