feat(proxy): T-P3 计价（峰谷窗口/毫元整数/差异化售价/黄金用例）

- pricing.py：is_offpeak（含跨午夜窗口、非法回落、±1min 边界语义）；
  compute 全整数毫元——上游成本叠加 offpeak_factor（空闲半价），
  学生售价按差异化折扣（in 0.5 / out 0.8，不叠加热闲系数，全天一口价），
  margin = charged - cost 恒等式
- 未配置价格模型三值零（调用方可拦截）；配置换算加载期唯一
- 测试 +9（窗口边界/跨午夜/回落/黄金手算 #1#2/恒等式 10 组扫/零用量/
  稳定性/未知模型/换算不漂移），全量 354 passed

tests/test_proxy_pricing.py

@@ -0,0 +1,131 @@
+"""计价测试（T-P3）：峰谷边界（假时钟 ±1 分钟）/ 毫元取整不漂移 / margin 恒等式。"""
+import time
+
+import pytest
+
+from gateway.proxy.config import ModelPrice, ProxyConfig, build_proxy_config
+from gateway.proxy.pricing import compute, is_offpeak
+from gateway.settings import DEFAULTS
+
+
+@pytest.fixture()
+def cfg():
+    return build_proxy_config(DEFAULTS)
+
+
+# ---------------- 峰谷窗口 ----------------
+
+def _ts(y, mo, d, h, mi):
+    return time.mktime((y, mo, d, h, mi, 0, 0, 0, -1))
+
+
+def test_offpeak_boundaries_plus_minus_one_minute():
+    """窗口 [08:30, 23:59]：边界 ±1 分钟翻转。"""
+    base = _ts(2026, 9, 1, 8, 29)
+    assert is_offpeak(base, "08:30", "23:59") is True             # 08:29 空闲
+    assert is_offpeak(base + 60, "08:30", "23:59") is False       # 08:30 高峰
+    base2 = _ts(2026, 9, 1, 23, 58)
+    assert is_offpeak(base2, "08:30", "23:59") is False           # 23:58 高峰
+    assert is_offpeak(base2 + 120, "08:30", "23:59") is True      # 00:00 次日空闲
+
+
+def test_offpeak_overnight_window():
+    """跨午夜窗口 [23:00, 06:00]：中午空闲、深夜高峰。"""
+    noon = _ts(2026, 9, 1, 12, 0)
+    deep = _ts(2026, 9, 1, 23, 30)
+    early = _ts(2026, 9, 1, 5, 59)
+    assert is_offpeak(noon, "23:00", "06:00") is True
+    assert is_offpeak(deep, "23:00", "06:00") is False
+    assert is_offpeak(early, "23:00", "06:00") is False
+
+
+def test_offpeak_invalid_window_falls_back():
+    """非法窗口回落默认 08:30-23:59。"""
+    noon = _ts(2026, 9, 1, 12, 0)
+    assert is_offpeak(noon, "garbage", "!!") is False
+    assert is_offpeak(_ts(2026, 9, 1, 7, 0), "garbage", "!!") is True
+
+
+# ---------------- 计算与取整 ----------------
+
+USAGE = {"in_miss": 3_000_000, "in_hit": 1_000_000, "out": 800_000}
+
+
+def test_compute_peak_math_exact(cfg):
+    """高峰：成本/售价逐项可手算（黄金用例 #1）。
+
+    deepseek-chat：in_miss=3000, in_hit=100, out=9000（毫元/1M）
+    成本 = 3M×3000/1M + 1M×100/1M + 0.8M×9000/1M = 9000+100+7200 = 16300 毫元
+    售价 = 9000×0.5 + 100×0.5 + 7200×0.8 = 4500+50+5760 = 10310 毫元
+    """
+    ts = _ts(2026, 9, 1, 12, 0)   # 高峰
+    r = compute(USAGE, "deepseek-chat", ts, cfg)
+    assert r["upstream_cost_milli"] == 16300
+    assert r["charged_milli"] == 10310
+    assert r["margin_milli"] == r["charged_milli"] - r["upstream_cost_milli"]
+
+
+def test_compute_offpeak_half_cost(cfg):
+    """空闲：上游成本半价（offpeak_factor=0.5），售价不变（黄金用例 #2）。"""
+    ts = _ts(2026, 9, 2, 3, 0)    # 空闲
+    r = compute(USAGE, "deepseek-chat", ts, cfg)
+    assert r["upstream_cost_milli"] == 8150            # 16300 × 0.5
+    assert r["charged_milli"] == 10310
+    assert r["margin_milli"] == 2160
+
+
+def test_margin_identity_holds_for_golden_cases(cfg):
+    """margin = charged - cost 恒等式（10 组黄金用例，量级/零/大数扫）。"""
+    ts = _ts(2026, 9, 1, 12, 0)
+    cases = [
+        {"in_miss": 0, "in_hit": 0, "out": 0},
+        {"in_miss": 1, "in_hit": 0, "out": 0},
+        {"in_miss": 0, "in_hit": 1, "out": 0},
+        {"in_miss": 0, "in_hit": 0, "out": 1},
+        {"in_miss": 1000, "in_hit": 0, "out": 0},
+        {"in_miss": 0, "in_hit": 1000, "out": 0},
+        {"in_miss": 0, "in_hit": 0, "out": 4096},
+        {"in_miss": 3500, "in_hit": 1500, "out": 800},
+        {"in_miss": 50_000, "in_hit": 10_000, "out": 10_000},   # 智能体任务
+        {"in_miss": 1_000_000, "in_hit": 1_000_000, "out": 100_000},
+    ]
+    for usage in cases:
+        r = compute(usage, "deepseek-chat", ts, cfg)
+        assert r["margin_milli"] == r["charged_milli"] - r["upstream_cost_milli"]
+        assert r["upstream_cost_milli"] >= 0 and r["charged_milli"] >= 0
+    # 零用量 -> 三值全零
+    assert compute(cases[0], "deepseek-chat", ts, cfg) == {
+        "upstream_cost_milli": 0, "charged_milli": 0, "margin_milli": 0}
+
+
+def test_no_drift_integer_only(cfg):
+    """取整不漂移：分项 round 后求和，重复计算结果稳定一致。"""
+    ts = _ts(2026, 9, 1, 12, 0)
+    usage = {"in_miss": 123_456, "in_hit": 65_432, "out": 7_777}
+    r1 = compute(usage, "deepseek-chat", ts, cfg)
+    r2 = compute(usage, "deepseek-chat", ts, cfg)
+    assert r1 == r2
+    for v in r1.values():
+        assert isinstance(v, int)
+
+
+def test_unknown_model_free(cfg):
+    """未配置价格的模型 -> 三值零（调用方可拦截）。"""
+    ts = _ts(2026, 9, 1, 12, 0)
+    assert compute(USAGE, "no-such-model", ts, cfg) == {
+        "upstream_cost_milli": 0, "charged_milli": 0, "margin_milli": 0}
+
+
+def test_config_milli_conversion_no_drift():
+    """配置换算唯一性：元/1M 浮点 -> 毫元/1M 整数只发生一次。"""
+    c = build_proxy_config({"proxy": {"pricing": {
+        "m1": {"in_miss": 0.003, "in_hit": 0.0001, "out": 0.009},
+        "m2": {"in_miss": 12.3456, "out": 1.5}}}})
+    assert c.price("m1").in_miss == 3
+    assert c.price("m1").in_hit == 1      # 0.0001 元 -> 0.1 毫元 -> 取整 0 -> 触发缺省 max(1, miss//30)
+    # in_hit 缺省 = in_miss//30（D-P3）：0.003 元 -> 3 毫元 -> 0（太小），显式补齐后重验
+    c2 = build_proxy_config({"proxy": {"pricing": {
+        "m1": {"in_miss": 3.0, "in_hit": 0.1, "out": 9.0},
+        "m2": {"in_miss": 12.3456, "out": 1.5}}}})
+    assert c2.price("m2").in_miss == 12346
+    assert c2.price("m2").in_hit == 12346 // 30        # 411