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_canonical.py

@@ -27,7 +27,7 @@ ALL_EVENTS = [
     GateOpened(gate="arch", reason="plan submitted (rev-1)"),
     DelegationStarted(
         brief="fix the flaky test",
-        role="delegate",
+        role="helper",
         model="claude-opus-5",
         caps={"turns": 20, "tokens": 100000},
     ),