Avoid overstating fallback AI bulletin reads

The city decision fallback path is generated when the full DeepSeek city-airport read has not completed, so the reasoning copy now labels the state as fast evidence mode instead of saying the AI read is normal.

Constraint: Fallback output may use only DEB, model cluster, and latest observation evidence

Rejected: Keep 'AI read normal' wording | it implies a completed AI interpretation when the fallback path is active

Confidence: high

Scope-risk: narrow

Tested: pytest tests/test_web_observability.py::test_city_ai_fallback_reasoning_identifies_fast_evidence_mode tests/test_web_observability.py::test_city_ai_partial_json_trims_dangling_taf_clause tests/test_web_observability.py::test_city_ai_schema_completion_trims_dangling_taf_clause -q

CHANGELOG.md

@@ -3,7 +3,7 @@
 ## 1.5.5 - 2026-04-27
 
 - 城市决策卡新增 AI 机场报文解读缓存说明：页面内存缓存保留 loading / 流式片段 / 最终结果，`localStorage` 保存最终成功 payload，后端 AI 缓存不再因 `local_time` 变化失效
-- 城市决策卡兜底文案明确为“AI 机场报文解读正常”，不再使用“AI 增强可后补 / 不阻塞”这类容易被误解为 AI 未解读的表述
+- 城市决策卡兜底文案明确标记“快速证据模式”，避免在 DeepSeek 未完整返回时误写成“AI 机场报文解读正常”
 - 城市决策卡市场层改用完整 `all_buckets` 并严格识别 exact / range / or higher / or lower 温度桶方向，避免最高温中枢错配到不合理尾部桶
 - 温度桶标签统一规范化 `C/F/°C/°F`，修复 `31°°C` 这类重复单位展示
 - 决策卡展示文案将“概率差”收口为“模型-市场差”，明确口径为 `模型概率 - 市场隐含概率`

tests/test_web_observability.py

@@ -100,7 +100,7 @@ def test_metrics_endpoint_returns_prometheus_payload():
     assert 'polyweather_http_requests_total' in response.text
 
 
-def test_city_ai_fallback_reasoning_says_ai_read_is_normal():
+def test_city_ai_fallback_reasoning_identifies_fast_evidence_mode():
     payload = scan_terminal_service._build_city_ai_fallback(
         {
             "city_display_name": "Tokyo",
@@ -128,7 +128,9 @@ def test_city_ai_fallback_reasoning_says_ai_read_is_normal():
         reason="preview",
     )
 
-    assert "AI 机场报文解读正常" in payload["reasoning_zh"]
+    assert "当前为快速证据模式" in payload["reasoning_zh"]
+    assert "完整 AI 机场报文解读返回后再合并" in payload["reasoning_zh"]
+    assert "AI 机场报文解读正常" not in payload["reasoning_zh"]
     assert "后补" not in payload["reasoning_zh"]
     assert "AI 增强可作为后续补充" not in payload["reasoning_zh"]
 

web/scan_terminal_service.py

@@ -720,12 +720,12 @@ def _build_city_ai_fallback(
     reasoning_zh = str(partial_ai.get("reasoning_zh") or "").strip() or (
         f"AI {bulletin_zh}解读已用于校准日内节奏；DEB 与多模型集合继续约束最高温中枢，后续{source_name_zh}用于确认是否需要上调或下修。"
         if partial_ai
-        else f"AI {bulletin_zh}解读正常；当前结合 DEB、多模型集合和最新{source_name_zh}，共同支撑本轮最高温中枢判断。"
+        else f"当前为快速证据模式；DEB、多模型集合和最新{source_name_zh}共同支撑本轮最高温中枢，完整 AI {bulletin_zh}解读返回后再合并。"
     )
     reasoning_en = str(partial_ai.get("reasoning_en") or "").strip() or (
         f"The AI {bulletin_en} read is already used to calibrate the intraday pace; DEB and the model cluster still constrain the high-temperature center, while later {source_name_en} updates confirm whether to revise it."
         if partial_ai
-        else f"The AI {bulletin_en} read is available; DEB, the model cluster and latest {source_name_en} jointly support the current daily-high center."
+        else f"This is the fast evidence mode; DEB, the model cluster and latest {source_name_en} jointly support the current daily-high center, and the full AI {bulletin_en} read will be merged when available."
     )
     risks_zh = [f"后续{source_name_zh}若明显偏离模型路径，需及时修正最高温中枢。"]
     risks_en = [f"If later {source_name_en} updates diverge from the model path, revise the daily-high center promptly."]