Fixed Memory Leaks in TransformerPipeline:
Replaced time.After(1 * time.Second) with a reusable time.NewTicker inside the Send() and startBlocking() loops. This prevents the allocation of thousands of lingering time.Timer objects during high-throughput syncs.

Fixed Goroutine Leaks in TransformerPipeline:
Introduced context.Context cancellation for the background Recv() goroutines. When the pipeline closes, the background goroutine now cleanly exits instead of being orphaned and blocking on a dead channel indefinitely.

Best-Effort Parallel Destination Shutdown:
Previously, destination cleanup in sync_v2.go and sync_v3.go was sequential and fail-fast. If the first destination failed to close, subsequent destinations were never closed (leaving dangling streams and missing summary data). This PR implements a parallel shutdown sequence using sync.WaitGroup, collecting all errors securely via sync.Mutex and errors.Join, ensuring all destinations attempt to close cleanly.

Plugin Timeout Propagation:
Previously, the CLI lacked timeout propagation for plugin lifecycle methods, meaning a stuck plugin would hang the entire CLI indefinitely. This PR introduces a --plugin-timeout CLI flag (defaulting to 0 for backward compatibility). It propagates a derived context to Init, Configure, Close, CloseAndRecv, and testPluginConnection gRPC calls to ensure the CLI can fail gracefully.