feat(api): wire /dm/narrate — 200 prose | 502 model_error | 422 invalid log

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

api/app/main.py

@@ -12,6 +12,8 @@ from fastapi.responses import JSONResponse
 from pydantic import BaseModel
 
 from .canon_log import validate_canon_log
+from .narrate import run as narrate_run
+from .ollama_client import ModelError
 
 app = FastAPI(title="coc-rpg proxy", version="0.0.1")
 
@@ -52,7 +54,10 @@ def health() -> dict:
 
 @app.post("/dm/narrate")
 def narrate(req: TurnRequest = Depends(valid_turn)) -> dict:
-    return {"detail": "not implemented"}
+    try:
+        return {"prose": narrate_run(req.canon_log)}
+    except ModelError as exc:
+        raise HTTPException(status_code=502, detail={"model_error": str(exc)})
 
 
 @app.post("/dm/adjudicate")