98fde82946
M3's row and §6 updated: the operator corpus is 125 cases across seven files, all green, and the pipeline work also gave `aggregate` the `$replaceWith` stage it never had -- the compiler is shared between the two. Full matrix at this commit: 249/249 unit tests in ReleaseFast and ReleaseSafe, 83/83 fuzz, operators 125/0, positional 51/0, aggregation 70/0, pinned crud 228/63/196, e2e and crash-fuzz green.