feat(telegram): add linkPreview config option

Add channels.telegram.linkPreview config to control whether link previews
are shown in outbound messages. When set to false, uses Telegram's
link_preview_options.is_disabled to suppress URL previews.

- Add linkPreview to TelegramAccountConfig type
- Add Zod schema validation for linkPreview
- Pass link_preview_options to sendMessage in send.ts and bot/delivery.ts
- Propagate linkPreview config through deliverReplies callers
- Add tests for link preview behavior

Fixes #1675

Co-Authored-By: Claude <noreply@anthropic.com>

src/telegram/bot/delivery.test.ts

@@ -108,4 +108,60 @@ describe("deliverReplies", () => {
       }),
     );
   });
+
+  it("includes link_preview_options when linkPreview is false", async () => {
+    const runtime = { error: vi.fn(), log: vi.fn() };
+    const sendMessage = vi.fn().mockResolvedValue({
+      message_id: 3,
+      chat: { id: "123" },
+    });
+    const bot = { api: { sendMessage } } as unknown as Bot;
+
+    await deliverReplies({
+      replies: [{ text: "Check https://example.com" }],
+      chatId: "123",
+      token: "tok",
+      runtime,
+      bot,
+      replyToMode: "off",
+      textLimit: 4000,
+      linkPreview: false,
+    });
+
+    expect(sendMessage).toHaveBeenCalledWith(
+      "123",
+      expect.any(String),
+      expect.objectContaining({
+        link_preview_options: { is_disabled: true },
+      }),
+    );
+  });
+
+  it("does not include link_preview_options when linkPreview is true", async () => {
+    const runtime = { error: vi.fn(), log: vi.fn() };
+    const sendMessage = vi.fn().mockResolvedValue({
+      message_id: 4,
+      chat: { id: "123" },
+    });
+    const bot = { api: { sendMessage } } as unknown as Bot;
+
+    await deliverReplies({
+      replies: [{ text: "Check https://example.com" }],
+      chatId: "123",
+      token: "tok",
+      runtime,
+      bot,
+      replyToMode: "off",
+      textLimit: 4000,
+      linkPreview: true,
+    });
+
+    expect(sendMessage).toHaveBeenCalledWith(
+      "123",
+      expect.any(String),
+      expect.not.objectContaining({
+        link_preview_options: expect.anything(),
+      }),
+    );
+  });
 });

src/telegram/bot/delivery.ts

@@ -36,8 +36,11 @@ export async function deliverReplies(params: {
   chunkMode?: ChunkMode;
   /** Callback invoked before sending a voice message to switch typing indicator. */
   onVoiceRecording?: () => Promise<void> | void;
+  /** Controls whether link previews are shown. Default: true (previews enabled). */
+  linkPreview?: boolean;
 }) {
-  const { replies, chatId, runtime, bot, replyToMode, textLimit, messageThreadId } = params;
+  const { replies, chatId, runtime, bot, replyToMode, textLimit, messageThreadId, linkPreview } =
+    params;
   const chunkMode = params.chunkMode ?? "length";
   const threadParams = buildTelegramThreadParams(messageThreadId);
   let hasReplied = false;
@@ -85,6 +88,7 @@ export async function deliverReplies(params: {
           messageThreadId,
           textMode: "html",
           plainText: chunk.text,
+          linkPreview,
         });
         if (replyToId && !hasReplied) {
           hasReplied = true;
@@ -180,6 +184,7 @@ export async function deliverReplies(params: {
             messageThreadId,
             textMode: "html",
             plainText: chunk.text,
+            linkPreview,
           });
           if (replyToId && !hasReplied) {
             hasReplied = true;
@@ -248,17 +253,22 @@ async function sendTelegramText(
     messageThreadId?: number;
     textMode?: "markdown" | "html";
     plainText?: string;
+    linkPreview?: boolean;
   },
 ): Promise<number | undefined> {
   const baseParams = buildTelegramSendParams({
     replyToMessageId: opts?.replyToMessageId,
     messageThreadId: opts?.messageThreadId,
   });
+  // Add link_preview_options when link preview is disabled.
+  const linkPreviewEnabled = opts?.linkPreview ?? true;
+  const linkPreviewOptions = linkPreviewEnabled ? undefined : { is_disabled: true };
   const textMode = opts?.textMode ?? "markdown";
   const htmlText = textMode === "html" ? text : markdownToTelegramHtml(text);
   try {
     const res = await bot.api.sendMessage(chatId, htmlText, {
       parse_mode: "HTML",
+      ...(linkPreviewOptions ? { link_preview_options: linkPreviewOptions } : {}),
       ...baseParams,
     });
     return res.message_id;
@@ -268,6 +278,7 @@ async function sendTelegramText(
       runtime.log?.(`telegram HTML parse failed; retrying without formatting: ${errText}`);
       const fallbackText = opts?.plainText ?? text;
       const res = await bot.api.sendMessage(chatId, fallbackText, {
+        ...(linkPreviewOptions ? { link_preview_options: linkPreviewOptions } : {}),
         ...baseParams,
       });
       return res.message_id;