[upstream #16875] Pin combined brand override precedence in the cache output #297

The resolver output pin in client/src/Providers/__tests__/themeCache.spec.ts generates one fixture per role and scope (theme-wide, light only, dark only), each overriding a single role. A definition that sets the same brand token theme-wide and per mode is not covered, so a precedence regression between the two would leave the pinned digest unchanged.

Fix direction: add a fixture per brand token with conflicting theme-wide, light and dark values, and check each persisted mode.