ci : switch from pyright to ty (#20826)

* type fixes

* switch to ty

* tweak rules

* tweak more rules

* more tweaks

* final tweak

* use common import-not-found rule

scripts/server-bench.py

@@ -189,6 +189,7 @@ def benchmark(
 
         data: list[dict] = []
 
+        assert isinstance(prompts, list)
         for i, p in enumerate(prompts):
             if seed_offset >= 0:
                 random.seed(3 * (seed_offset + 1000 * i) + 1)