Add RegisterLocalSnapshot and GetRemoteSnapshotMetadata methods

Introduce methods to register local snapshots from archives and to download or restore snapshot metadata, improving snapshot management capabilities. Update README with usage examples.

README.md

@@ -223,6 +223,41 @@ func main() {
 
 ## Advanced Usage
 
+### Registering a Local Snapshot
+
+You can register a local snapshot from an existing archive file with a specified UUID:
+
+```go
+// Register a local snapshot from an archive file
+archivePath := "/path/to/your/archive.zip"
+snapshotID := "custom-uuid-for-snapshot"
+snapshotName := "My Local Snapshot"
+
+if err := ag.RegisterLocalSnapshot(ctx, archivePath, snapshotID, snapshotName); err != nil {
+    log.Fatalf("Failed to register local snapshot: %v", err)
+}
+```
+
+### Downloading Only Snapshot Metadata
+
+You can download only the metadata of a snapshot from a remote server without downloading the actual files:
+
+```go
+// Download only the metadata of a snapshot from a remote server
+remoteAddress := "remote-server:50051"
+snapshotID := "snapshot-id-to-download"
+
+if err := ag.GetRemoteSnapshotMetadata(ctx, remoteAddress, snapshotID); err != nil {
+    log.Fatalf("Failed to download snapshot metadata: %v", err)
+}
+
+// If you have a local blob but missing metadata, you can restore the metadata
+// by passing an empty address
+if err := ag.GetRemoteSnapshotMetadata(ctx, "", snapshotID); err != nil {
+    log.Fatalf("Failed to restore snapshot metadata: %v", err)
+}
+```
+
 ### Creating Incremental Snapshots
 
 You can create incremental snapshots by specifying a parent snapshot ID:
@@ -294,6 +329,8 @@ The main entry point for the library.
 - `ConnectRemote(address string) (*grpc.SnapshotClient, error)` - Connect to a remote server
 - `GetRemoteSnapshotList(ctx context.Context, address string) ([]store.SnapshotInfo, error)` - List snapshots from a remote server
 - `GetRemoteSnapshot(ctx context.Context, address string, snapshotID string, localParentID string) error` - Download a snapshot from a remote server
+- `RegisterLocalSnapshot(ctx context.Context, archivePath string, snapshotID string, name string) error` - Register a local snapshot from an archive path with a specified UUID
+- `GetRemoteSnapshotMetadata(ctx context.Context, address string, snapshotID string) error` - Download only the metadata of a snapshot from a remote server
 
 ### AgateOptions
 
@@ -304,7 +341,3 @@ Configuration options for the Agate library.
 - `CloseFunc func() error` - Called before a snapshot is created or restored
 - `MetadataStore store.MetadataStore` - Implementation of the metadata store
 - `BlobStore store.BlobStore` - Implementation of the blob store
-
-## License
-
-[Add your license information here]