chore: add ty + pre-commit hook and repeal even more ruff rules (#9504)

* auto fixes

* auto fix pt2 and transitive deps and undefined var checking locals()

* manual fixes (ignored or letta-code fixed)

* fix circular import

* remove all ignores, add FastAPI rules and Ruff rules

* add ty and precommit

* ruff stuff

* ty check fixes

* ty check fixes pt 2

* error on invalid

tests/test_letta_agent_batch.py

@@ -1,4 +1,5 @@
 import asyncio
+import itertools
 from datetime import datetime, timezone
 from typing import Tuple
 from unittest.mock import AsyncMock, patch
@@ -769,7 +770,7 @@ def _assert_descending_order(messages):
     if len(messages) <= 1:
         return True
 
-    for prev, next in zip(messages[:-1], messages[1:]):
+    for prev, next in itertools.pairwise(messages):
         assert prev.created_at >= next.created_at, (
             f"Order violation: {prev.id} ({prev.created_at}) followed by {next.id} ({next.created_at})"
         )