Roles, capability profiles and help on the new loop (M2.6)

- roles.driver (unset: the planner's model) and roles.classifier (unset:
  the expert's); the mapping is pinned when an item opens, and the driver
  and the go-ahead reader run on the item's own (L9).
- profiles: in configuration (tools, strengths, weaknesses), used in
  briefings: the driver's instructions say what its helper and expert are
  good at, the helper's brief who reads its handback; never a model name.
- delegate(task) and ask_expert(question) for the driver. A helper works
  on a branch off the milestone's; on a handback its work comes back as
  uncommitted changes, otherwise it is discarded, so harness branches
  never hold commits only the clone has. ask_expert keeps its budget.
- Triggers: failure_limit failed commands in a row (Driver's new "stuck"
  outcome) or the turn cap, mid-milestone, call a helper in once per
  milestone; if it fails too, the item waits on the operator. A
  delegation cut off by a crash is discarded at boot.
- Evaluation capture: delegations and ask_expert as before, and the
  reader's verdicts as classifier pairs.

Tests: help tests (merge-back, discard, needs a milestone, the stuck
trigger and its once-per-milestone limit, the expert and its budget,
pinning, briefings by profile, boot discarding a cut-off delegation),
config tests for roles and profiles, and the walk delegating with a
scripted helper that sometimes fails, with a delegations_settle property.
The walk found helper commits stranded on a merged PR's branch, fixed by
returning a helper's work uncommitted.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPQ14L3LikyefCMFBqEbKE

nisse-dev/tests/test_config.py

@@ -478,3 +478,29 @@ def test_a_workspace_of_any_project_inside_is_refused(tmp_path: Path) -> None:
             state_db=str(work / "state.db"),
             projects__other={**SECOND, "workspace": str(work)},
         )
+
+
+# --- roles and profiles (L9) -------------------------------------------------
+
+
+def test_the_new_loops_roles_fall_back() -> None:
+    config = build()
+    assert config.roles.resolve("driver") == "claude-opus-5"  # the planner's
+    assert config.roles.resolve("classifier") == "claude-haiku-4-5"  # the expert's
+    named = build(roles__driver="qwen3.8-27b", roles__classifier="gemma-4-12b")
+    assert named.roles.resolve("driver") == "qwen3.8-27b"
+    assert named.roles.pinned()["classifier"] == "gemma-4-12b"
+
+
+def test_capability_profiles_are_read() -> None:
+    config = build(
+        profiles={"qwen3.8-27b": {"tools": "reliable", "weaknesses": "speed"}}
+    )
+    profile = config.profiles["qwen3.8-27b"]
+    assert profile.describe() == "tool calls: reliable; weak at speed"
+    assert build().profiles == {}
+
+
+def test_a_bad_profile_is_reported() -> None:
+    with pytest.raises(ConfigError, match="profiles.m.colour: unknown setting"):
+        build(profiles={"m": {"colour": "red"}})