feat(api): config + role→model routing (qwen3.5 narrator default, think off)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

api/tests/test_routing.py

@@ -0,0 +1,21 @@
+import pytest
+
+from app.routing import for_role
+
+
+def test_narrator_defaults():
+    cfg = for_role("narrator")
+    assert cfg.model == "qwen3.5:latest"
+    assert cfg.think is False
+    assert cfg.options["num_predict"] == 300
+    assert cfg.options["temperature"] == 0.8
+
+
+def test_env_overrides_model(monkeypatch):
+    monkeypatch.setenv("OLLAMA_NARRATOR_MODEL", "llama3.1:latest")
+    assert for_role("narrator").model == "llama3.1:latest"
+
+
+def test_unknown_role_raises():
+    with pytest.raises(KeyError):
+        for_role("wizard")