Rename the delegate and consultant roles to helper and expert

Architecture L9's role names, for the two roles with a direct
counterpart: the delegation role is now 'helper' and the ask_expert role
'expert', in RoleMap, configuration (roles.helper, roles.expert),
recorded events and tests. 'planner' and 'executor' stay distinct for
now; they become 'driver' when the new loop merges them (Development
Plan M2.3).

Configurations must rename their keys: nisse-dev.example.yaml and
tests/integration/nisse-test.yaml are updated here.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPQ14L3LikyefCMFBqEbKE

nisse-dev/tests/test_approvals.py

@@ -20,7 +20,7 @@ from nisse_dev.planner import LLMPlanningAgent
 from nisse_dev.state import StateStore
 from nisse_dev.transport import InMemoryTransport
 
-ROLES = RoleMap(executor="x", planner="y", delegate="y", consultant="y")
+ROLES = RoleMap(executor="x", planner="y", helper="y", expert="y")
 
 
 class FakeGitea: