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/expert.py

@@ -17,7 +17,7 @@ memory: it survives a restart, and it is observable from outside the model,
 which is the same reasoning L9 applies to escalation triggers.
 
 Consults are recorded as ``delegation_started`` / ``delegation_completed`` with
-role ``consultant``. That is deliberate — L9 wants a "consult/delegation eval
+role ``expert``. That is deliberate — L9 wants a "consult/delegation eval
 set", and reusing the composite events gets consult evaluation for free rather
 than inventing a parallel record.
 """
@@ -35,7 +35,7 @@ from nisse_dev.canonical import (
 from nisse_dev.llm import LLMClient, LLMError, RoleMap
 from nisse_dev.state import StateStore
 
-CONSULTANT_ROLE = "consultant"
+EXPERT_ROLE = "expert"
 DEFAULT_BUDGET = 3
 
 SYSTEM_PROMPT = """You are a consultant answering one self-contained question.
@@ -111,8 +111,7 @@ class ExpertDesk:
         return sum(
             1
             for e in self._store.read_events(after=since_event_id)
-            if isinstance(e.event, DelegationStarted)
-            and e.event.role == CONSULTANT_ROLE
+            if isinstance(e.event, DelegationStarted) and e.event.role == EXPERT_ROLE
         )
 
     def ask(self, question: str, *, since_event_id: int = 0) -> ExpertAnswer:
@@ -122,11 +121,11 @@ class ExpertDesk:
                 f"consult budget of {self._budget} is spent for this task "
                 f"({used} used); escalate or ask the operator instead"
             )
-        model = self._roles.resolve(CONSULTANT_ROLE)
+        model = self._roles.resolve(EXPERT_ROLE)
         self._store.append_event(
             DelegationStarted(
                 brief=question,
-                role=CONSULTANT_ROLE,
+                role=EXPERT_ROLE,
                 model=model,
                 caps={"consults": self._budget, "used": used},
             )