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/src/nisse_dev/bench/runner.py

@@ -174,7 +174,7 @@ def run_task(
         meter = MeteringClient(client, facts)
         trims_before = getattr(client, "trimmed_requests", 0)
         model = facts.alias
-        roles = RoleMap(executor=model, planner=model, delegate=model, consultant=model)
+        roles = RoleMap(executor=model, planner=model, helper=model, expert=model)
         executor = LLMExecutor(
             meter,
             store,