fix: update remaining replyToMode "first" defaults to "off"

- src/channels/dock.ts: core channel dock fallback
- src/auto-reply/reply/reply-routing.test.ts: test expectation
- docs/zh-CN/channels/telegram.md: Chinese docs reference

Comprehensive grep confirms no remaining Telegram-specific "first"
defaults after this commit.

docs/zh-CN/channels/telegram.md

@@ -724,7 +724,7 @@ Telegram 反应作为**单独的 `message_reaction` 事件**到达，而不是
   - `channels.telegram.groups.<id>.topics.<threadId>.requireMention`：每话题提及门控覆盖。
 - `channels.telegram.capabilities.inlineButtons`：`off | dm | group | all | allowlist`（默认：allowlist）。
 - `channels.telegram.accounts.<account>.capabilities.inlineButtons`：每账户覆盖。
-- `channels.telegram.replyToMode`：`off | first | all`（默认：`first`）。
+- `channels.telegram.replyToMode`：`off | first | all`（默认：`off`）。
 - `channels.telegram.textChunkLimit`：出站分块大小（字符）。
 - `channels.telegram.chunkMode`：`length`（默认）或 `newline` 在长度分块之前按空行（段落边界）分割。
 - `channels.telegram.linkPreview`：切换出站消息的链接预览（默认：true）。

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

@@ -158,8 +158,8 @@ describe("createReplyDispatcher", () => {
 });
 
 describe("resolveReplyToMode", () => {
-  it("defaults to first for Telegram", () => {
-    expect(resolveReplyToMode(emptyCfg, "telegram")).toBe("first");
+  it("defaults to off for Telegram", () => {
+    expect(resolveReplyToMode(emptyCfg, "telegram")).toBe("off");
   });
 
   it("defaults to off for Discord and Slack", () => {

src/channels/dock.ts

@@ -115,7 +115,7 @@ const DOCKS: Record<ChatChannelId, ChannelDock> = {
       resolveToolPolicy: resolveTelegramGroupToolPolicy,
     },
     threading: {
-      resolveReplyToMode: ({ cfg }) => cfg.channels?.telegram?.replyToMode ?? "first",
+      resolveReplyToMode: ({ cfg }) => cfg.channels?.telegram?.replyToMode ?? "off",
       buildToolContext: ({ context, hasRepliedRef }) => {
         const threadId = context.MessageThreadId ?? context.ReplyToId;
         return {