chore: ruff auto-fix PLR6201 — tuple → set in membership tests (#23937)

Replace  with  for all literal-tuple
membership tests. Set lookup is O(1) vs O(n) for tuple — consistent
micro-optimization across the codebase.

608 instances fixed via `ruff --fix --unsafe-fixes`, 0 remaining.
133 files, +626/-626 (net zero).

tools/todo_tool.py

@@ -109,7 +109,7 @@ class TodoStore:
         # cause the model to re-do finished work after compression.
         active_items = [
             item for item in self._items
-            if item["status"] in ("pending", "in_progress")
+            if item["status"] in {"pending", "in_progress"}
         ]
         if not active_items:
             return None