added pandoc as renderer

src/markdown_utils.py

@@ -3,6 +3,7 @@ from __future__ import annotations
 import re
 
 import markdown as md_lib
+import subprocess
 
 from .errors import ValidationIssue
 
@@ -81,5 +82,22 @@ def convert_markdown(
         except Exception as exc:  # pragma: no cover - depends on markdown internals
             issues.append(ValidationIssue(f"Markdown conversion failed: {exc}", context=context))
             return None
+    if renderer == "pandoc":
+        try:
+            result = subprocess.run(
+                ["pandoc", "--from=markdown", "--to=html5"],
+                input=markdown_text,
+                text=True,
+                capture_output=True,
+                check=True,
+            )
+            return result.stdout
+        except FileNotFoundError as exc:
+            issues.append(ValidationIssue(f"pandoc is not available: {exc}", context=context))
+            return None
+        except subprocess.CalledProcessError as exc:
+            stderr = exc.stderr.strip() if exc.stderr else ""
+            issues.append(ValidationIssue(f"Pandoc conversion failed: {stderr}", context=context))
+            return None
     issues.append(ValidationIssue(f"Unknown renderer: {renderer}", context=context))
     return None