Tenth review pass: adding unexported chunkRun/chunkMoves fields to Request broke source compatibility for embedders using positional struct literals (and made the struct impossible to fully construct outside the package). The chunk state now travels in an internal runOptions argument threaded to abridgeOne and buildUserPrompt; Request's exported shape is unchanged from before the series, pinned by a positional-literal test. Co-authored-by: Shelley <shelley@exe.dev>