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_agent_build.py

@@ -263,7 +263,7 @@ def test_a_tool_less_model_warns_but_still_boots(tmp_path: Path, monkeypatch) ->
     logged = stream.getvalue()
     assert "model_tools_unsupported" in logged
     assert '"role": "executor"' in logged
-    assert '"role": "consultant"' not in logged  # ask_expert drives no tools
+    assert '"role": "expert"' not in logged  # ask_expert drives no tools
 
 
 def test_the_resolved_model_is_pinned_at_task_start(