Sync-first runtime layer for batpak-family operation surfaces.
```text
sb runs.
```
`syncbat` owns operation descriptors, handler registration, checkout dispatch,
runtime receipts, and durable operation-catalog rows through batpak public APIs.
It does not own network framing, async runtimes, application kit vocabulary, or
batpak store internals.
The runtime contract is documented in repository ADR-0028.