Switch to JWT token for inference against Nous, falling back to old opaque token on failure.

tests/conftest.py

@@ -187,6 +187,7 @@ _HERMES_BEHAVIORAL_VARS = frozenset({
     "HERMES_BACKGROUND_NOTIFICATIONS",
     "HERMES_EXEC_ASK",
     "HERMES_HOME_MODE",
+    "HERMES_AGENT_USE_LEGACY_SESSION_KEYS",
     # Kanban path/board pins must never leak from a developer shell or
     # dispatched worker into tests; otherwise tests can write fake tasks to
     # the real ~/.hermes/kanban.db instead of the per-test HERMES_HOME.