Define cache invalidation from user-visible examples

Inputs: [CACHE KEYS], [MUTATIONS], [READ PATHS]. For each write identify affected cache entries, ordering and race windows. Specify a safe fallback when invalidation fails. Output: A mutation-to-key map and reproducible stale-read tests. Check: Test whether a completed update can stay hidden by an old entry beyond the stated consistency window; mark guarantees unproven until the tests run under realistic concurrency. If essential information is missing, identify it rather than guessing.