fix(zulip): add _strip_html for slash command matching

Zulip delivers message content as HTML (<p>/approve</p>).
The gateway slash command parser expects plain text, so HTML
tags prevent command matching. This helper strips HTML tags
and decodes common entities (&amp;, &lt;, etc.).

Per contract: zulip-approval-fix.prose.md

Applied to: Mumuni (CT114), Tanko (CT112), Koby (CT111)

plugins/platforms/zulip/adapter.py

@@ -99,6 +99,23 @@ def _build_auth_header(email: str, api_key: str) -> str:
     return f"Basic {token}"
 
 
+def _strip_html(text: str) -> str:
+    """Strip HTML tags and decode HTML entities from Zulip message content.
+
+    Zulip delivers message content as rendered HTML (e.g. <p>/approve</p>).
+    The gateway slash command parser expects plain text, so HTML tags
+    prevent command matching. This helper strips tags and decodes entities.
+    """
+    if not text:
+        return text
+    # Strip HTML tags
+    text = re.sub(r"<[^>]+>", "", text)
+    # Decode common HTML entities
+    text = text.replace("&amp;", "&").replace("&lt;", "<").replace("&gt;", ">")
+    text = text.replace("&quot;", '"').replace("&#39;", "'").replace("&nbsp;", " ")
+    return text.strip()
+
+
 def _truncate(text: str, limit: int = MAX_ZULIP_MESSAGE) -> str:
     """Truncate to Zulip's message limit with notice."""
     if len(text) <= limit:
@@ -784,6 +801,8 @@ class ZulipAdapter(BasePlatformAdapter):
         sender_name = msg.get("sender_full_name", "Unknown")
         sender_id = msg.get("sender_id")
         content = msg.get("content", "")
+        # Strip Zulip HTML for slash command matching (zulip-approval-fix contract)
+        content = _strip_html(content)
 
         # Echo-loop prevention: skip own messages
         if sender_email == self._bot_email: