fix: refine group intro prompt guidance

docs/concepts/groups.md

@@ -212,7 +212,7 @@ Group inbound payloads set:
 - `WasMentioned` (mention gating result)
 - Telegram forum topics also include `MessageThreadId` and `IsForum`.
 
-The agent system prompt includes a group intro on the first turn of a new group session.
+The agent system prompt includes a group intro on the first turn of a new group session. It reminds the model to respond like a human, avoid Markdown tables, and avoid typing literal `\n` sequences.
 
 ## iMessage specifics
 - Prefer `chat_id:<id>` when routing or allowlisting.

src/auto-reply/reply.triggers.test.ts

@@ -2015,7 +2015,7 @@ describe("trigger handling", () => {
 
 describe("group intro prompts", () => {
   const groupParticipationNote =
-    "Be a good group participant: mostly lurk and follow the conversation; reply only when directly addressed or you can add clear value. Emoji reactions are welcome when available.";
+    "Be a good group participant: mostly lurk and follow the conversation; reply only when directly addressed or you can add clear value. Emoji reactions are welcome when available. Write like a human. Avoid Markdown tables. Don't type literal \\n sequences; use real line breaks sparingly.";
   it("labels Discord groups using the surface metadata", async () => {
     await withTempHome(async (home) => {
       vi.mocked(runEmbeddedPiAgent).mockResolvedValue({

src/auto-reply/reply/groups.ts

@@ -94,6 +94,8 @@ export function buildGroupIntro(params: {
       : undefined;
   const lurkLine =
     "Be a good group participant: mostly lurk and follow the conversation; reply only when directly addressed or you can add clear value. Emoji reactions are welcome when available.";
+  const styleLine =
+    "Write like a human. Avoid Markdown tables. Don't type literal \\n sequences; use real line breaks sparingly.";
   return [
     subjectLine,
     membersLine,
@@ -102,6 +104,7 @@ export function buildGroupIntro(params: {
     silenceLine,
     cautionLine,
     lurkLine,
+    styleLine,
   ]
     .filter(Boolean)
     .join(" ")