long term memory plug-in

Key features

• Stores durable memory in a local Git repository, not in this source repository or a hosted service.
• A host-side operation lock ( /.sync/operation.lock) serializes sync and rollback operations.
• dsh-memory-sync --preview captures the candidate diff (baseline plus model edits) as a pending preview under /.sync/previews/ with a 7-day expiry, without applying anything.
• Record ids may be namespaced with a single / (project/codegen, user/preferences)
• Registers the memory settings namespace immediately, so memory.enabled takes effect for the next model call without restarting DSH.