feat: transcript restart script (#742)

* transcript restart script

* fix tests?

* remove useless comment

---------

Co-authored-by: Igor Loskutov <igor.loskutoff@gmail.com>

server/reflector/utils/match.py

@@ -0,0 +1,10 @@
+from typing import NoReturn
+
+
+def assert_exhaustiveness(x: NoReturn) -> NoReturn:
+    """Provide an assertion at type-check time that this function is never called."""
+    raise AssertionError(f"Invalid value: {x!r}")
+
+
+def absurd(x: NoReturn) -> NoReturn:
+    return assert_exhaustiveness(x)