fix(drift): drift_narrator 改用 OpenClaw AI Router — 修復「研判原因」空白

根因：drift_narrator_service.py 的 _generate_narrative() 直接呼叫
      Ollama httpx (192.168.0.111:11434)，繞過 AI Router，無 fallback。
      192.168.0.111 為死亡 IP → httpx 連線失敗 → 降級 fallback_narrative()
      → fallback 中 interpretation.explanation 存在但顯示層截斷 → 空白

修復：改用 get_openclaw().call(prompt)，統一走 AI Router
      同 drift_interpreter.py 的修法（d952435）
      移除 unused httpx import

2026-04-17 ogt + Claude Sonnet 4.6

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/api/src/services/drift_narrator_service.py

@@ -19,11 +19,11 @@ from __future__ import annotations
 
 from typing import TYPE_CHECKING
 
-import httpx
 import structlog
 
 from src.core.redis_client import get_redis
 from src.services.model_registry import get_model
+from src.services.openclaw import get_openclaw
 
 if TYPE_CHECKING:
     from src.models.drift import DriftInterpretation, DriftReport
@@ -156,25 +156,19 @@ class DriftNarratorService:
             intent_summary=intent_summary,
         )
 
+        # 2026-04-17 ogt + Claude Sonnet 4.6: 改用 OpenClaw AI Router 取代直接 Ollama httpx
+        # 根因：直接呼叫 192.168.0.111:11434 繞過 AI Router，無 fallback → "All connection attempts failed"
+        # 修復：統一走 openclaw.call()，自動享有 Provider 降級與 fallback 機制
+        # 同 drift_interpreter.py 的修法（d952435）
         try:
-            async with httpx.AsyncClient(timeout=NARRATOR_TIMEOUT) as client:
-                resp = await client.post(
-                    f"{OLLAMA_URL}/api/generate",
-                    json={
-                        "model": NARRATOR_MODEL,
-                        "prompt": prompt,
-                        "stream": False,
-                        "options": {"temperature": 0.3, "num_predict": 300},
-                    },
-                )
-                resp.raise_for_status()
-                data = resp.json()
-                text = data.get("response", "").strip()
-                if text:
-                    return text
+            openclaw = get_openclaw()
+            text, _provider, success = await openclaw.call(prompt)
+
+            if success and text and text.strip():
+                return text.strip()
+
+            logger.warning("drift_narrator_openclaw_failed", provider=_provider)
 
-        except httpx.TimeoutException:
-            logger.warning("drift_narrator_timeout", model=NARRATOR_MODEL)
         except Exception as e:
             logger.warning("drift_narrator_llm_error", error=str(e))