fix(reply): auto-inject replyToCurrent for reply threading

replyToMode "first"/"all" only filters replyToId but never generates
it — that required the LLM to emit [[reply_to_current]] tags. Inject
replyToCurrent:true on all payloads so applyReplyTagsToPayload sets
replyToId=currentMessageId, then let the existing mode filter decide
which replies keep threading (first only, all, or off).

Covers both final reply path (reply-payloads.ts) and block streaming
path (agent-runner-execution.ts).

src/auto-reply/reply/reply-payloads.ts

@@ -63,7 +63,9 @@ export function applyReplyThreading(params: {
   const { payloads, replyToMode, replyToChannel, currentMessageId } = params;
   const applyReplyToMode = createReplyToModeFilterForChannel(replyToMode, replyToChannel);
   return payloads
-    .map((payload) => applyReplyTagsToPayload(payload, currentMessageId))
+    .map((payload) =>
+      applyReplyTagsToPayload({ ...payload, replyToCurrent: true }, currentMessageId),
+    )
     .filter(isRenderablePayload)
     .map(applyReplyToMode);
 }