fix: initialize affinity_token before the turn-lease early returns

The turn-lease timeout/interrupt paths return from inside the try block
before set_affinity_scope() runs; the finally then read an unassigned
local -> UnboundLocalError. This was the cause of the 4 red
cross-process lease tests on PR #97158's CI.

(cherry picked from commit 05a3c8a4caa59831b01d13f3950e61385aadbfa5)

run_agent.py

@@ -9067,6 +9067,11 @@ class AIAgent:
         durable_turn_lease_turn_active = False
         durable_turn_lease_interrupt_message = None
         token = None
+        # Initialized alongside `token`: the turn-lease timeout/interrupt
+        # early returns leave the try block before set_affinity_scope() runs,
+        # and the finally reads this name unconditionally (UnboundLocalError
+        # otherwise — the 4 red cross-process lease tests on PR #97158).
+        affinity_token = None
         acct_token = None
         task_started = False
         task_finished = False