feat(sense): T-G1 Embedder（int8 量化/降级 fail-closed + /v1/embeddings 透传）

- embedder.py：embed() 调 llama-server /v1/embeddings -> 对称 per-vector
  int8 量化（scale=127/max|v|，1024 维余弦扰动 ~1e-4 << 1e-2 验收）；
  超时/连接/非200/空形状 -> EmbedderDown（D-G4 fail-closed）；
  quantize_int8/cosine_int8 辅助（int8 直接点积，scale 正标量不改方向）
- routes.py 拆双路由组：/sense 前缀组 + /v1 无前缀组（/v1/embeddings
  OpenAI 兼容透传，embedder 不可用 503）；build_sense_routers 返回列表，
  api.py 逐个 include；build_sense_router 保留向后兼容
- 测试 +6：量化余弦误差 200 组 <1e-2/范围/零向量/int8 余弦/
  正常量化/三种 fail-closed/透传端点（503+形状+400），全量 381 passed
- 待真机项：llama-server embedder 端点冒烟（需用户配置 embedder.base_url）

tests/test_sense_embedder.py

@@ -0,0 +1,148 @@
+"""Embedder 测试（T-G1）：int8 量化余弦误差 / 降级 fail-closed / 透传端点。"""
+import asyncio
+import json
+import math
+import random
+
+import httpx
+import pytest
+
+pytest.importorskip("fastapi")
+
+from fastapi import FastAPI
+from fastapi.testclient import TestClient
+
+from gateway.sense.config import EmbedderCfg, build_sense_config
+from gateway.sense.embedder import cosine_int8, embed, quantize_int8
+from gateway.sense.errors import EmbedderDown
+
+
+def test_quantize_roundtrip_cosine_error_small():
+    """200 组 1024 维随机向量：量化前后余弦误差 < 1e-2（§11 验收）。"""
+    random.seed(42)
+    worst = 0.0
+    for _ in range(200):
+        v = [random.gauss(0, 1) for _ in range(1024)]
+        q = quantize_int8(v)
+        scale = (max(abs(x) for x in v) and 127.0 / max(abs(x) for x in v)) or 1.0
+        dv = [x / scale for x in q]
+        err = 1.0 - cosine_int8(q, quantize_int8(v))   # 自反性恒 1；此行检对称
+        # 真误差：原向量 vs 反量化向量
+        dot = sum(a * b for a, b in zip(v, dv))
+        na = math.sqrt(sum(a * a for a in v))
+        nb = math.sqrt(sum(b * b for b in dv))
+        err = 1.0 - dot / (na * nb)
+        worst = max(worst, abs(err))
+    assert worst < 1e-2
+
+
+def test_quantize_range_and_zero_vector():
+    q = quantize_int8([3.0, -6.0, 0.0])
+    assert all(-127 <= x <= 127 for x in q)
+    assert quantize_int8([0.0] * 4) == [0, 0, 0, 0]      # 零向量不崩
+
+
+def test_cosine_int8_identical_and_orthogonal():
+    assert cosine_int8([3, 4], [6, 8]) == pytest.approx(1.0)
+    assert cosine_int8([1, 0], [0, 1]) == 0.0
+    assert cosine_int8([], []) == 0.0
+
+
+def _cfg(base_url="http://emb"):
+    return EmbedderCfg(base_url=base_url, model="bge-m3", timeout_s=1.0, dim=8)
+
+
+def test_embed_ok_returns_int8(monkeypatch):
+    vec = [0.5 * i for i in range(1, 9)]
+    body = {"data": [{"embedding": vec}]}
+
+    def handler(request: httpx.Request) -> httpx.Response:
+        assert request.url.path == "/embeddings"
+        payload = json.loads(request.read())
+        assert payload["model"] == "bge-m3" and payload["input"] == "hello"
+        return httpx.Response(200, content=json.dumps(body).encode())
+
+    import gateway.sense.embedder as em
+    orig = em._client
+    em._client = httpx.AsyncClient(transport=httpx.MockTransport(handler))
+    try:
+        q = asyncio_run(embed("hello", _cfg()))
+        assert len(q) == 8 and all(-127 <= x <= 127 for x in q)
+    finally:
+        em._client = orig
+
+
+def test_embed_down_fail_closed(monkeypatch):
+    """连接拒绝/非 200/超时 -> EmbedderDown（D-G4 fail-closed）。"""
+    from gateway.sense import embedder as em
+
+    def handler_500(request):
+        return httpx.Response(500)
+
+    orig = em._client
+    em._client = httpx.AsyncClient(transport=httpx.MockTransport(handler_500))
+    try:
+        with pytest.raises(EmbedderDown):
+            asyncio_run(embed("x", _cfg()))
+    finally:
+        em._client = orig
+
+    def handler_timeout(request):
+        raise httpx.ConnectTimeout("超时")
+
+    em._client = httpx.AsyncClient(transport=httpx.MockTransport(handler_timeout))
+    try:
+        with pytest.raises(EmbedderDown):
+            asyncio_run(embed("x", _cfg()))
+    finally:
+        em._client = orig
+
+    def handler_bad_shape(request):
+        return httpx.Response(200, content=json.dumps({"data": [{"embedding": []}]}).encode())
+
+    em._client = httpx.AsyncClient(transport=httpx.MockTransport(handler_bad_shape))
+    try:
+        with pytest.raises(EmbedderDown):
+            asyncio_run(embed("x", _cfg()))
+    finally:
+        em._client = orig
+
+
+def test_v1_embeddings_endpoint(tmp_path):
+    """enabled 独立挂载：/v1/embeddings 透传（Mock embedder 注入）。"""
+    tc_app = FastAPI()
+    cfg = build_sense_config({"sense": {"enabled": True,
+                                        "db_path": str(tmp_path / "s.sqlite3")}})
+    from gateway.sense.routes import build_sense_routers
+    app = FastAPI()
+    for r in build_sense_routers(cfg):
+        app.include_router(r)
+    client = TestClient(app)
+
+    # embedder 不可用 -> 503 fail-closed
+    r = client.post("/v1/embeddings", json={"input": "hello"})
+    assert r.status_code == 503
+
+    # 注入可用 embedder（monkeypatch 内部函数）
+    import gateway.sense.routes as sr
+    orig_embed = sr.embed
+
+    async def fake_embed(text, c):
+        return [1, 2, 3]
+
+    sr.embed = fake_embed
+    try:
+        r2 = client.post("/v1/embeddings", json={"input": "hello"})
+        assert r2.status_code == 200
+        data = r2.json()
+        assert data["object"] == "list"
+        assert data["data"][0]["embedding"] == [1, 2, 3]
+        # 空 input -> 400
+        r3 = client.post("/v1/embeddings", json={"input": ""})
+        assert r3.status_code == 400
+    finally:
+        sr.embed = orig_embed
+
+
+def asyncio_run(coro):
+    return asyncio.run(coro)