fix: avoid duplicate block streaming

docs/agent.md

@@ -82,7 +82,7 @@ current turn ends, then a new agent turn starts with the queued payloads. See
 
 Block streaming sends completed assistant blocks as soon as they finish; disable
 via `agent.blockStreamingDefault: "off"` if you only want the final response.
-Tune the boundary via `agent.blockStreamingBreak` (`text_end` vs `message_end`).
+Tune the boundary via `agent.blockStreamingBreak` (`text_end` vs `message_end`; defaults to text_end).
 Control soft block chunking with `agent.blockStreamingChunk` (defaults to
 800–1200 chars; prefers paragraph breaks, then newlines; sentences last).