mesofact-dev 0.8.34

Dev-tier affordances for mesofact workloads — a rebuild-on-change watcher, a local S3 surface standing in for R2, and `mesofact_dev::serve_app`, the dev half of a library-tier project's two bin targets. The serving engine lives in the `mesofact` facade; this crate must never be in a prod binary's dependency closure (W225 §2).