slack: use slackify-markdown for proper mrkdwn formatting

Replace the regex-based Markdown-to-Slack converter with the
slackify-markdown library, which uses a proper Markdown parser
(markdown-it-py, already a dependency) to correctly handle headings,
bold/italic, code blocks, links, bullet lists, and strikethrough.

The regex approach didn't handle headings (###), bullet lists (* ),
or code block protection, causing raw Markdown to leak into Slack
messages.

Net -40 lines.

Assisted-by: Claude 4.6 Opus (Anthropic)

nanobot/channels/slack.py

@@ -10,6 +10,8 @@ from slack_sdk.socket_mode.request import SocketModeRequest
 from slack_sdk.socket_mode.response import SocketModeResponse
 from slack_sdk.web.async_client import AsyncWebClient
 
+from slackify_markdown import slackify_markdown
+
 from nanobot.bus.events import OutboundMessage
 from nanobot.bus.queue import MessageBus
 from nanobot.channels.base import BaseChannel
@@ -84,7 +86,7 @@ class SlackChannel(BaseChannel):
             use_thread = thread_ts and channel_type != "im"
             await self._web_client.chat_postMessage(
                 channel=msg.chat_id,
-                text=self._convert_markdown(msg.content) or "",
+                text=slackify_markdown(msg.content) if msg.content else "",
                 thread_ts=thread_ts if use_thread else None,
             )
         except Exception as e:
@@ -204,46 +206,3 @@ class SlackChannel(BaseChannel):
             return text
         return re.sub(rf"<@{re.escape(self._bot_user_id)}>\s*", "", text).strip()
 
-    # Markdown → Slack mrkdwn formatting rules (order matters: longest markers first)
-    _MD_TO_SLACK = (
-        (r'(?m)(^|[^\*])\*\*\*(.+?)\*\*\*([^\*]|$)', r'\1*_\2_*\3'),  # ***bold italic***
-        (r'(?m)(^|[^_])___(.+?)___([^_]|$)', r'\1*_\2_*\3'),            # ___bold italic___
-        (r'(?m)(^|[^\*])\*\*(.+?)\*\*([^\*]|$)', r'\1*\2*\3'),          # **bold**
-        (r'(?m)(^|[^_])__(.+?)__([^_]|$)', r'\1*\2*\3'),                # __bold__
-        (r'(?m)(^|[^\*])\*(.+?)\*([^\*]|$)', r'\1_\2_\3'),              # *italic*
-        (r'(?m)(^|[^~])~~(.+?)~~([^~]|$)', r'\1~\2~\3'),                # ~~strike~~
-        (r'(?m)(^|[^!])\[(.+?)\]\((http.+?)\)', r'\1<\3|\2>'),          # [text](url)
-        (r'!\[.+?\]\((http.+?)(?:\s".*?")?\)', r'<\1>'),                # ![alt](url)
-    )
-    _TABLE_RE = re.compile(r'(?m)^\|.*?\|$(?:\n(?:\|\:?-{3,}\:?)*?\|$)(?:\n\|.*?\|$)*')
-
-    def _convert_markdown(self, text: str) -> str:
-        """Convert standard Markdown to Slack mrkdwn format."""
-        if not text:
-            return text
-        for pattern, repl in self._MD_TO_SLACK:
-            text = re.sub(pattern, repl, text)
-        return self._TABLE_RE.sub(self._convert_table, text)
-
-    @staticmethod
-    def _convert_table(match: re.Match) -> str:
-        """Convert Markdown table to Slack quote + bullet format."""
-        lines = [l.strip() for l in match.group(0).strip().split('\n') if l.strip()]
-        if len(lines) < 2:
-            return match.group(0)
-
-        headers = [h.strip() for h in lines[0].strip('|').split('|')]
-        start = 2 if not re.search(r'[^|\-\s:]', lines[1]) else 1
-
-        result: list[str] = []
-        for line in lines[start:]:
-            cells = [c.strip() for c in line.strip('|').split('|')]
-            cells = (cells + [''] * len(headers))[:len(headers)]
-            if not any(cells):
-                continue
-            result.append(f"> *{headers[0]}*: {cells[0] or '--'}")
-            for i, cell in enumerate(cells[1:], 1):
-                if cell and i < len(headers):
-                    result.append(f"  \u2022 *{headers[i]}*: {cell}")
-            result.append("")
-        return '\n'.join(result).rstrip()

pyproject.toml

@@ -36,6 +36,7 @@ dependencies = [
     "python-socketio>=5.11.0",
     "msgpack>=1.0.8",
     "slack-sdk>=3.26.0",
+    "slackify-markdown>=0.2.0",
     "qq-botpy>=1.0.0",
     "python-socks[asyncio]>=2.4.0",
     "prompt-toolkit>=3.0.0",