fix: never split replies into multiple messages (Fabric has no length limit)

Unlike Discord, Fabric has no message-length cap. Single-chunk chunker
(text -> [text]), textChunkLimit=MAX_SAFE_INTEGER, capabilities
blockStreaming=false, replyOptions.disableBlockStreaming=true -> every
agent reply delivered as exactly one Fabric message.

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

dist/fabric/src/inbound.js

@@ -144,7 +144,8 @@ export class FabricInbound {
                 },
                 onRecordError: (err) => this.log.warn(`fabric: session record failed agent=${agentId}: ${String(err)}`),
                 onDispatchError: (err, info) => this.log.warn(`fabric: ${info.kind} dispatch failed agent=${agentId}: ${String(err)}`),
-                replyOptions: {},
+                // Fabric has no length limit: deliver the whole reply as ONE message.
+                replyOptions: { disableBlockStreaming: true },
             });
             this.log.info(`fabric: dispatch returned agent=${agentId} channel=${channelId}`);
         }