feat(channel): render Markdown as HTML in Telegram messages

Claude Code responses use Markdown formatting (bold, italic, code blocks,
inline code) which Telegram displays as raw text by default.

Add markdownToHtml() converter in TelegramAdapter that transforms standard
Markdown to Telegram HTML, and send messages with parse_mode: 'HTML'.
Code blocks are extracted first to prevent formatting replacements inside them.

Author: BrookLe

packages/channel-connector/src/adapters/TelegramAdapter.ts

@@ -59,7 +59,8 @@ export class TelegramAdapter implements ChannelAdapter {
     async sendMessage(chatId: string, text: string): Promise<void> {
         const chunks = chunkMessage(text, TELEGRAM_MAX_MESSAGE_LENGTH);
         for (const chunk of chunks) {
-            await this.bot.telegram.sendMessage(chatId, chunk);
+            const html = markdownToHtml(chunk);
+            await this.bot.telegram.sendMessage(chatId, html, { parse_mode: 'HTML' });
         }
     }
 
@@ -108,3 +109,44 @@ function chunkMessage(text: string, maxLen: number): string[] {
 
     return chunks;
 }
+
+function escapeHtml(text: string): string {
+    return text.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;');
+}
+
+/**
+ * Convert standard Markdown to Telegram HTML.
+ * Handles code blocks first to prevent formatting inside them.
+ */
+function markdownToHtml(text: string): string {
+    const codeBlocks: string[] = [];
+    const inlineCodes: string[] = [];
+
+    let result = text.replace(/```(\w*)\n?([\s\S]*?)```/g, (_, lang, code) => {
+        const escaped = escapeHtml(code.trimEnd());
+        const block = lang
+            ? `<pre><code class="language-${lang}">${escaped}</code></pre>`
+            : `<pre><code>${escaped}</code></pre>`;
+        codeBlocks.push(block);
+        return `\x00CODE${codeBlocks.length - 1}\x00`;
+    });
+
+    result = result.replace(/`([^`]+)`/g, (_, code) => {
+        inlineCodes.push(`<code>${escapeHtml(code)}</code>`);
+        return `\x00INLINE${inlineCodes.length - 1}\x00`;
+    });
+
+    result = escapeHtml(result);
+
+    result = result
+        .replace(/\*\*(.+?)\*\*/g, '<b>$1</b>')
+        .replace(/__(.+?)__/g, '<b>$1</b>')
+        .replace(/\*(.+?)\*/g, '<i>$1</i>')
+        .replace(/_(.+?)_/g, '<i>$1</i>')
+        .replace(/~~(.+?)~~/g, '<s>$1</s>');
+
+    result = result.replace(/\x00CODE(\d+)\x00/g, (_, i) => codeBlocks[parseInt(i)]);
+    result = result.replace(/\x00INLINE(\d+)\x00/g, (_, i) => inlineCodes[parseInt(i)]);
+
+    return result;
+}