Go: implement Encode (embeddings) in Aliyun driver (#14647)

### What problem does this PR solve?

The Aliyun Go driver shipped with a stub \`Encode\` method that returned
\`no such method\`, even though \`conf/models/aliyun.json\` already
wires the OpenAI-compatible embeddings URL suffix at
\`compatible-mode/v1/embeddings\`. The same config also did not list any
embedding models, so the picker had nothing to select.

So an Aliyun tenant who wanted to use Tongyi text-embedding-v3 or v4 in
the Go layer could not, even though the upstream endpoint is public and
uses the standard \`POST /v1/embeddings\` shape that the SiliconFlow and
ZhipuAI
drivers already support.

This PR fills the gap.

### What this PR includes

- \`conf/models/aliyun.json\`: add \`text-embedding-v4\` and
\`text-embedding-v3\` to the \`models\` array.
- \`internal/entity/models/aliyun.go\`: replace the \`Encode\` stub with
a real implementation. Adds a small local response type that matches the
OpenAI-compatible shape.

No factory change. No interface change.

### How the driver works

- Validate \`apiConfig\` and the API key, validate the model name,
resolve the region with a default fallback, build the
  URL from \`BaseURL[region] + URLSuffix.Embedding\`.
- Send all input texts in one request as the \`input\` array, the same
OpenAI-compatible shape the SiliconFlow \`Encode\`
  uses.
- Parse \`data[*].embedding\` and copy each slice into a \`[][]float64\`
indexed by \`data[*].index\` so the output order matches the input order
even if the API returns items in a different order.
- Handle both \`float64\` and \`float32\` element types.
- Empty input returns \`[][]float64{}\` with no HTTP call.
- Non-200 responses propagate the upstream status line and body.
- A final pass checks every input slot got a vector and returns a clear
error if any slot is still nil.

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

### How was this tested?

- \`go build ./internal/entity/models/...\` in a clean go 1.25 image
returns exit 0.
- The full method set on \`AliyunModel\` still matches the
\`ModelDriver\` interface.
- Pattern parity with the existing SiliconFlow Encode implementation.

Closes #14646

---------

Co-authored-by: Jin Hai <haijin.chn@gmail.com>

conf/models/aliyun.json

@@ -17,6 +17,20 @@
       "model_types": [
         "chat"
       ]
+    },
+    {
+      "name": "text-embedding-v4",
+      "max_tokens": 8192,
+      "model_types": [
+        "embedding"
+      ]
+    },
+    {
+      "name": "text-embedding-v3",
+      "max_tokens": 8192,
+      "model_types": [
+        "embedding"
+      ]
     }
   ],
   "features": {

internal/entity/models/aliyun.go

@@ -19,6 +19,7 @@ package models
 import (
 	"bufio"
 	"bytes"
+	"context"
 	"encoding/json"
 	"fmt"
 	"io"
@@ -350,9 +351,111 @@ func (z *AliyunModel) ChatStreamlyWithSender(modelName string, messages []Messag
 	return scanner.Err()
 }
 
+type aliyunEmbeddingResponse struct {
+	Data []struct {
+		Index     int           `json:"index"`
+		Embedding []interface{} `json:"embedding"`
+	} `json:"data"`
+}
+
 // Encode encodes a list of texts into embeddings
 func (z *AliyunModel) Encode(modelName *string, texts []string, apiConfig *APIConfig, embeddingConfig *EmbeddingConfig) ([][]float64, error) {
-	return nil, fmt.Errorf("%s, no such method", z.Name())
+	if len(texts) == 0 {
+		return [][]float64{}, nil
+	}
+
+	if apiConfig == nil || apiConfig.ApiKey == nil || *apiConfig.ApiKey == "" {
+		return nil, fmt.Errorf("api key is required")
+	}
+
+	if modelName == nil || *modelName == "" {
+		return nil, fmt.Errorf("model name is required")
+	}
+
+	region := "default"
+	if apiConfig.Region != nil && *apiConfig.Region != "" {
+		region = *apiConfig.Region
+	}
+
+	baseURL := z.BaseURL["default"]
+	if region != "default" {
+		if regional, ok := z.BaseURL[region]; ok && regional != "" {
+			baseURL = regional
+		}
+	}
+	if baseURL == "" {
+		return nil, fmt.Errorf("aliyun: no base URL configured for default region")
+	}
+
+	url := fmt.Sprintf("%s/%s", strings.TrimSuffix(baseURL, "/"), z.URLSuffix.Embedding)
+
+	reqBody := map[string]interface{}{
+		"model": *modelName,
+		"input": texts,
+	}
+
+	jsonData, err := json.Marshal(reqBody)
+	if err != nil {
+		return nil, fmt.Errorf("failed to marshal request: %w", err)
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+	defer cancel()
+
+	req, err := http.NewRequestWithContext(ctx, "POST", url, bytes.NewBuffer(jsonData))
+	if err != nil {
+		return nil, fmt.Errorf("failed to create request: %w", err)
+	}
+
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("Authorization", fmt.Sprintf("Bearer %s", *apiConfig.ApiKey))
+
+	resp, err := z.httpClient.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("failed to send request: %w", err)
+	}
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read response: %w", err)
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("Aliyun embeddings API error: %s, body: %s", resp.Status, string(body))
+	}
+
+	var parsed aliyunEmbeddingResponse
+	if err = json.Unmarshal(body, &parsed); err != nil {
+		return nil, fmt.Errorf("failed to parse response: %w", err)
+	}
+
+	embeddings := make([][]float64, len(texts))
+	for _, item := range parsed.Data {
+		if item.Index < 0 || item.Index >= len(texts) {
+			return nil, fmt.Errorf("unexpected embedding index %d for %d inputs", item.Index, len(texts))
+		}
+		vec := make([]float64, len(item.Embedding))
+		for j, v := range item.Embedding {
+			switch val := v.(type) {
+			case float64:
+				vec[j] = val
+			case float32:
+				vec[j] = float64(val)
+			default:
+				return nil, fmt.Errorf("unexpected embedding value type at item %d index %d", item.Index, j)
+			}
+		}
+		embeddings[item.Index] = vec
+	}
+
+	for i, vec := range embeddings {
+		if vec == nil {
+			return nil, fmt.Errorf("missing embedding for input at index %d", i)
+		}
+	}
+
+	return embeddings, nil
 }
 
 // Rerank calculates similarity scores between query and texts