test: prove native reconnect recovery

internal/client/agent/runner.go

@@ -35,6 +35,10 @@ type RunnerOptions struct {
 	OnSignal      func(context.Context, Session, *rvboxv1.SignalCommand) error
 	OnScriptReady func(context.Context, Session, domain.UUID) error
 	OnTerminate   func(context.Context, domain.UUID) error
+	// OnSessionError observes one failed dial, handshake, protocol, or active
+	// transport session before normal reconnect backoff. It must not block; the
+	// durable spool and retry policy remain owned by Run.
+	OnSessionError func(error)
 	// EventReady wakes the active session after a supervisor worker appends a
 	// durable event. The network loop remains the sole writer; a reconnect can
 	// safely ignore a stale notification because replay reads the spool again.
@@ -95,10 +99,13 @@ func Run(ctx context.Context, options RunnerOptions) error {
 			return nil
 		}
 		sessionStarted := options.Now()
-		_ = runOnce(ctx, options)
+		sessionErr := runOnce(ctx, options)
 		if ctx.Err() != nil {
 			return nil
 		}
+		if sessionErr != nil && options.OnSessionError != nil {
+			options.OnSessionError(sessionErr)
+		}
 		if options.Now().Sub(sessionStarted) >= options.Backoff.StableReset {
 			failures = 0
 		}
@@ -344,17 +351,17 @@ func serveActive(ctx context.Context, transport Transport, options RunnerOptions
 		switch {
 		case envelope.GetCommandDispatch() != nil:
 			if err := handleDispatch(ctx, transport, options, session, envelope.GetCommandDispatch(), limits); err != nil {
-				return err
+				return fmt.Errorf("handle command dispatch %s: %w", envelope.GetCommandDispatch().GetIssueUuid(), err)
 			}
 			issue, parseErr := domain.ParseUUIDv7(envelope.GetCommandDispatch().GetIssueUuid())
 			if parseErr == nil {
 				if err := flushEvents(ctx, transport, options.Store, session, issue, limits, sent); err != nil {
-					return err
+					return fmt.Errorf("flush dispatched command %s events: %w", issue, err)
 				}
 			}
 		case envelope.GetEventAck() != nil:
 			if err := ApplyEventAck(ctx, options.Store, envelope.GetEventAck()); err != nil {
-				return err
+				return fmt.Errorf("apply event acknowledgement for %s: %w", envelope.GetEventAck().GetIssueUuid(), err)
 			}
 		case envelope.GetScriptChunk() != nil:
 			if err := handleScriptChunk(ctx, transport, options.Store, session, envelope.GetScriptChunk(), limits, options.Now, sent); err != nil {