Add pack diff command

mcp_server.py

@@ -89,6 +89,12 @@ def pack_build(
     )
 
 
+@mcp.tool()
+def pack_diff(left: str, right: str) -> dict[str, Any]:
+    """Diff two directories and/or .m2p archives using normalized paths and plaintext hashes."""
+    return _run_cli("diff", "--left", left, "--right", right)
+
+
 @mcp.tool()
 def pack_list(archive: str) -> dict[str, Any]:
     """List entries in an .m2p archive."""