feat(proxy): T-X13 采纳 ai-model-router 五维评分选模——能力过滤后确定性排序 + 拒绝理由留痕

- routes：能力位硬过滤（T-X6 语义不变）后对存活候选五维评分——
  cost_efficiency=1/(1+均价*2)、capability=上下文余量（不满足为 0）、
  speed/quality=档位秩比互补（local 快 / premium 优）、reliability 权重占位；
  重定向目标从'取首元素'改为'取最高分'；降级链按评分降序稳定重排
- 被淘汰候选带人话拒绝理由（vision/tools/上下文窗口三类）写入评分留痕环
  （deque 上限 100），/admin/stats 新增 route_scored 段透出（管理面可观测）
- 硬过滤语义不变：评分只改变链内顺序，不改变谁能存活
- 新增 tests/test_route_score.py 4 项（拒绝理由/排序偏好/同分决胜/留痕）

tests/test_route_score.py

@@ -0,0 +1,62 @@
+"""五维评分选模与拒绝理由留痕（T-X13，采纳 ai-model-router scoring 设计）。"""
+import gateway.proxy.routes as R
+from gateway.proxy.routes import (_entry_reject_reason, _rank_candidates,
+                                  _record_route_score_event,
+                                  reset_route_score_events)
+
+
+def _entry(model, tier="budget", price_in=1.0, price_out=2.0,
+           vision=True, tools=True, ctx=0):
+    return {"id": model, "model": model, "enabled": True,
+            "backend": "openai", "base_url": "http://127.0.0.1:9/v1",
+            "tier": tier, "price_in": price_in, "price_out": price_out,
+            "capabilities": {"vision": vision, "tools": tools,
+                             "context_window": ctx}}
+
+
+_NEEDS = {"vision": True, "tools": False, "min_context_tokens": 1000}
+
+
+def test_reject_reasons_are_human_readable():
+    """vision/tools/上下文三类不满足均有对应人话理由；满足则 None。"""
+    assert "vision" in (_entry_reject_reason(_entry("a", vision=False), _NEEDS) or "")
+    need_tools = {"vision": False, "tools": True, "min_context_tokens": 1000}
+    assert "tools" in (_entry_reject_reason(_entry("a", tools=False), need_tools) or "")
+    small = _entry("a", ctx=512)
+    assert "512" in (_entry_reject_reason(small, _NEEDS) or "")
+    assert _entry_reject_reason(_entry("a", ctx=8192), _NEEDS) is None
+
+
+def test_rank_prefers_capable_and_cheap():
+    """不满足需求者 capability=0 沉底；便宜者靠成本效率维胜出。"""
+    good_cheap = _entry("cheap", tier="budget", price_in=0.1, price_out=0.2, ctx=8192)
+    good_pricey = _entry("pricey", tier="premium", price_in=8.0, price_out=8.0, ctx=8192)
+    ranked = _rank_candidates([good_pricey, good_cheap], _NEEDS)
+    assert ranked[0]["model"] == "cheap"
+    assert ranked[0]["dims"]["capability"] > 0
+    assert ranked[0]["dims"]["cost_efficiency"] > ranked[1]["dims"]["cost_efficiency"]
+    # premium 的质量维更高（启发式）
+    assert ranked[1]["dims"]["quality"] > ranked[0]["dims"]["quality"]
+
+
+def test_rank_tie_break_deterministic():
+    """同配置同分按模型名字典序。"""
+    a, b = _entry("zeta"), _entry("alpha")
+    ranked = _rank_candidates([a, b], _NEEDS)
+    assert [s["model"] for s in ranked] == ["alpha", "zeta"]
+
+
+def test_score_event_records_rejections():
+    """评分留痕：入选排序 + 被淘汰候选的拒绝理由；reset 清空。"""
+    reset_route_score_events()
+    ranked = _rank_candidates([_entry("good", ctx=8192)], _NEEDS)
+    rejected = [{"model": "bad", "reason": "模型不支持视觉输入（vision）"}]
+    _record_route_score_event("px-test", ranked, rejected)
+    _record_route_score_event("px-test-2", ranked, rejected)
+    assert len(R._route_score_events) == 2
+    ev = R._route_score_events[-1]
+    assert ev["request_id"] == "px-test-2"
+    assert ev["ranked"][0]["model"] == "good"
+    assert ev["rejected"][0]["reason"].startswith("模型不支持")
+    reset_route_score_events()
+    assert len(R._route_score_events) == 0