Resolve Client.Go-002, -003 code-review findings

Client.Go-002: the Events/EventsAfter compatibility path silently dropped
events when the 16-slot results channel filled — it cancelled the stream and
closed the channel with no error delivered. sendEventResult now evicts an
old buffered event and delivers a terminal EventResult carrying the new
exported ErrEventBufferOverflow before close, so the overflow is observable.

Client.Go-003: parseInt32List panicked on a malformed -item-handles token,
crashing the CLI with a stack trace. It now returns an error that
runUnsubscribeBulk propagates, exiting 2 with a clean message.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

clients/go/README.md

@@ -79,7 +79,13 @@ client, err := mxgateway.Dial(ctx, mxgateway.Options{
 `AddItem`, `AddItem2`, `Advise`, `Write`, `Events`, and `Close`. Prefer
 `SubscribeEvents` or `SubscribeEventsAfter` for long-running streams because the
 returned subscription owns cancellation and exposes `Close` for deterministic
-goroutine cleanup. Raw protobuf messages remain available through the
+goroutine cleanup. `Events` and `EventsAfter` are a compatibility shim with a
+bounded internal buffer: if the consumer drains too slowly the buffer fills,
+the underlying stream is cancelled, and a terminal `EventResult` carrying
+`ErrEventBufferOverflow` is delivered as the channel's last item before it
+closes — so a slow consumer can distinguish dropped events from a normal
+end-of-stream. `SubscribeEvents` blocks instead of dropping, so use it when no
+events may be lost. Raw protobuf messages remain available through the
 `mxgateway` package aliases and the `Raw` helper methods. Typed errors support
 `errors.As` for `GatewayError`, `CommandError`, and `MxAccessError`; command
 errors preserve the raw reply.