fix(matrix): preserve mxc markdown image sources

nanobot/channels/matrix.py

@@ -18,7 +18,7 @@ from nanobot.security.workspace_policy import is_path_within
 try:
     import aiohttp
     import nh3
-    from mistune import create_markdown
+    from mistune import HTMLRenderer, create_markdown
     from nio import (
         AsyncClient,
         AsyncClientConfig,
@@ -77,7 +77,7 @@ class _MediaTooLargeError(Exception):
     """Raised when an inbound Matrix media download exceeds the configured cap."""
 
 MATRIX_MARKDOWN = create_markdown(
-    escape=True,
+    renderer=HTMLRenderer(escape=True, allow_harmful_protocols=("mxc://",)),
     plugins=["table", "strikethrough", "url", "superscript", "subscript"],
 )