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/agent.py

@@ -37,7 +37,7 @@ from nisse_dev.worker import SerialWorker
 # manager allows for a stop, and a hard exit mid-work is already safe.
 SHUTDOWN_WAIT_S = 10.0
 
-TOOL_DRIVING_ROLES = ("planner", "executor", "delegate")
+TOOL_DRIVING_ROLES = ("planner", "executor", "helper")
 
 
 def discover_models(config: AgentConfig, oplog: OpLog) -> ModelCatalog:
@@ -220,7 +220,7 @@ def build_agent(
     expert = ExpertDesk(
         normalized, store, config.roles, budget=tuning.expert.consult_budget
     )
-    delegate_model = config.roles.resolve("delegate")
+    delegate_model = config.roles.resolve("helper")
     delegation = Delegation(
         select_client(delegate_model, normalized, passthrough, catalog),
         store,