fix: reject a trailing newline in sudo; test: malformed input suite

src/aegis_gitea_mcp/gitea/encoding.py

@@ -273,7 +273,8 @@ def validate_sudo(sudo: Any) -> str | None:
     """Validate the optional ``sudo`` login (None when not given)."""
     if sudo is None:
         return None
-    if not isinstance(sudo, str) or not _SUDO_PATTERN.match(sudo):
+    # fullmatch: ``$`` would also accept a trailing newline.
+    if not isinstance(sudo, str) or not _SUDO_PATTERN.fullmatch(sudo):
         raise ArgumentError("sudo must be a Gitea username (letters, digits, '-', '_', '.')")
     return sudo