feat(grpc): add earliest/latest block height to GetSyncing response

[Cordtus]

Description

This PR extends the GetSyncingResponse in cosmos.base.tendermint.v1beta1.Service to include block height information that is essential for indexers and tooling.

Problem

Indexers need to know which blocks are available on a node before attempting to fetch them. Currently, this information is only available via CometBFT's /status RPC endpoint (sync_info.earliest_block_height), requiring clients to query two different endpoints.

When an indexer tries to fetch a pruned block, it gets an error like:

height 60 is not available, lowest height is 28566001

Discovering available block heights proactively via gRPC would be more efficient.

Solution

Add two new fields to GetSyncingResponse:

• earliest_block_height - The earliest block height available on this node
• latest_block_height - The latest block height available on this node

These fields expose the same information as CometBFT's SyncInfo struct, making it available via the existing gRPC endpoint without requiring a separate RPC call.

Changes

File	Change
proto/cosmos/base/tendermint/v1beta1/query.proto	Add new fields to GetSyncingResponse
client/grpc/cmtservice/query.pb.go	Generated code with new fields
client/grpc/cmtservice/service.go	Populate new fields from SyncInfo

API

message GetSyncingResponse {
  bool syncing = 1;
  int64 earliest_block_height = 2;  // NEW
  int64 latest_block_height = 3;    // NEW
}

Backward Compatibility

This is a non-breaking change - it only adds new optional fields to an existing response message. Existing clients will continue to work unchanged.

Use Case

// Before: Need to query CometBFT RPC separately
status, _ := rpcClient.Status(ctx)
earliest := status.SyncInfo.EarliestBlockHeight

// After: Available via gRPC
resp, _ := cmtClient.GetSyncing(ctx, &GetSyncingRequest{})
earliest := resp.EarliestBlockHeight