feat: carry caller dimensions down the embedding chain

EmbeddingClient does not go through the chat onion: it builds its own
ChatRequest inside _emit purely to reuse the shared TelemetryEmitter, so
wiring chat() alone left every embed row without a tenant. Validate the
dimensions at the embed() entry (before batching, since anything failing
further down is degraded to a warning) and thread them through
_embed_batch -> _attempt -> _emit so every batch row carries the same
pair.

tests/unit/test_embedding.py

@@ -412,6 +412,45 @@ class TestEmbedTelemetry:
         assert len(rec.rows[1]["messages"]) < 1000  # 长文本截断后入库
 
 
+class TestEmbedCallerDimensions:
+    """issue #11: 调用方自定义维度必须沿 embed 链四层透传到每一行遥测。"""
+
+    async def test_single_batch_row_carries_dimensions(self):
+        rec = _MemoryRecorder()
+        client, _ = _embed_client([_src()], ["ok"], batch_size=2, telemetry=rec)
+        await client.embed(["a"], tenant_id="t1", meta={"batch": "b-42"})
+        assert rec.rows[0]["tenant_id"] == "t1"
+        assert rec.rows[0]["meta"] == '{"batch": "b-42"}'
+
+    async def test_every_batch_row_carries_the_same_dimensions(self):
+        """维度属于本次 `embed()` 调用,不随批次变化。
+
+        只断言首行会漏掉"只有第一批带维度"的实现——那正是逐层透传最容易漏的形态。
+        """
+        rec = _MemoryRecorder()
+        client, _ = _embed_client([_src()], ["ok", "ok", "ok"], batch_size=1, telemetry=rec)
+        await client.embed(["a", "b", "c"], tenant_id="t1", meta={"batch": "b-42"})
+        assert len(rec.rows) == 3  # 切成三批,每批一行
+        assert [r["tenant_id"] for r in rec.rows] == ["t1", "t1", "t1"]
+        assert [r["meta"] for r in rec.rows] == ['{"batch": "b-42"}'] * 3
+
+    async def test_invalid_meta_rejected_before_any_telemetry(self):
+        """校验在切批之前: 遥测层的失败都被降级成 warning,放下游等于没有校验。"""
+        rec = _MemoryRecorder()
+        client, _ = _embed_client([_src()], ["ok"], batch_size=2, telemetry=rec)
+        with pytest.raises(ValueError, match="meta"):
+            await client.embed(["a"], meta={"Bad Key": 1})
+        assert rec.rows == []
+        assert client._transport.calls == []  # 连调用都没发出
+
+    async def test_defaults_land_as_sentinels(self):
+        rec = _MemoryRecorder()
+        client, _ = _embed_client([_src()], ["ok"], batch_size=2, telemetry=rec)
+        await client.embed(["a"])
+        assert rec.rows[0]["tenant_id"] == ""  # 空串哨兵,不是 None
+        assert rec.rows[0]["meta"] == "{}"
+
+
 @contextlib.contextmanager
 def _captured_warnings():
     """捕获库发出的 WARNING;loguru 不经标准 logging,pytest 的 caplog 抓不到。"""