docs(apiproxy): state the export queue bound exactly

The response stream uses a fixed 64 KiB byte high-water mark; no deployment setting controls it. Calling that queue configured incorrectly suggested another tuning surface and obscured the concrete memory bound.\n\nName the fixed capacity directly while preserving the separate bound of one synchronous fflate push beyond the queued bytes.

packages/host/apiproxy/src/session-export.ts

@@ -15,7 +15,7 @@
  * bytes are produced incrementally and the host never holds the whole archive
  * in one buffer; production waits for consumer pull whenever the response queue
  * reaches its byte high-water mark, so a slow consumer bounds accumulation to
- * the configured queue plus one synchronous fflate push.
+ * the fixed 64 KiB response queue plus one synchronous fflate push.
  * @module
  */