Module backend 

MemBackend — uniform trait surface over folder, git-branch, and archive storage.

Bytes-level: list / read / write / delete / move / commit / append-provenance / read-provenance. The one-engine architecture that the workspace-store rebuild produces sits above this trait; entity-mutation logic, validation, the in-memory store, and the search index live in one place regardless of which backend serves a given mount.

Today’s crate::storage::MemWriter is a write-side subset of this trait. As each backend gains its MemBackend impl the MemWriter references in that backend’s call sites collapse into the unified surface; MemWriter stays in crate::storage::filesystem for now as the on-disk write helpers it embodies are reused by the folder-backend MemBackend impl.

Per-backend write semantics

• Folder — writes go to the workspace’s mem subdirectory; commit is a no-op CAS-token mint (no history).
• Git-branch — writes buffer in memory, commit produces a real git commit on the per-mem branch with the trailer block.
• Archive — writes return BackendError::Sealed without touching disk. Read methods return live content from inside the sealed .mem zip.

Enums

BackendError

Errors surfaced by MemBackend.

Traits

MemBackend

Mem-backend trait. Implementations live next to the backend’s other code (folder under crate::storage::filesystem; git-branch in the renamed-from-memstead-git-branch crate; archive under the archive read-paths in crate::entity once that wiring lands).