All /b/ routing removed from pathType, read, remove, handleWrite,
readDir, and makeStat. The batchStore field is gone from Server;
SessionStore now handles both session and batch job lifecycle.
-154 lines from server.go.
- Replace Get/Put calls with storeRead/storeWrite helpers
- Replace Wait calls with storeBlockingRead helper
- Wrapper types override Open instead of Get
- Use OpenStore for session/batch child stores
- All store fields typed as Store
- FlatDirStore alias points to BlobStore
- Server fields use BlobStore for flat stores
- Replace JobStore/SessionFileStore with Open
- Type-assert for Wait/LogInfo where needed
- Rename store variable to sfs to avoid package shadowing