Define the SeaweedParquetPushdown gRPC service with two RPCs (Ping,
Pushdown) and the request/response messages from the design's API
sketch (DataFileDescriptor, DeleteFileRef, ColumnRef, VectorQuery,
PushdownStats, ...). Includes the discriminator enums (DeleteContent,
FileFormat, PredicateKind, VectorMetric).
Add the Makefile rule mirroring the iam.proto / mq_agent.proto
pattern (paths=source_relative, output to weed/pb/parquet_pushdown_pb).
Commit the generated .pb.go and _grpc.pb.go alongside; the existing
plugin_pb / mount_peer_pb directories follow the same checked-in
generated-code convention.
No service implementation yet — that's M0-C2.
Chris Lu
2e423c0f31