Fix(Go): make Baidu Encode fail loudly on malformed responses (#14721)

### What problem does this PR solve?

The Baidu (Qianfan) `Encode` method silently swallowed malformed
responses. If a `data[]` item from the API was missing a field (`index`,
`embedding`, or unexpected shape), the loop did `continue` instead of
returning an error, leaving `nil` entries in the result slice. Callers
got back partial results with no indication anything went wrong, which
then crashes downstream consumers when they try to use a `nil` vector.

Concrete gaps fixed:

- No count-mismatch check between `data` length and input texts (only
checked for empty)
- No duplicate-index detection (a duplicate would silently overwrite)
- No missing-index final scan
- No empty-embedding rejection
- No per-call context timeout
- `EmbeddingConfig.Dimension` (added in #14735) was not propagated

This PR replaces `map[string]interface{}` parsing with a typed
`baiduEmbeddingResponse` struct, applies the standard four-layer
validation (count → out-of-range → duplicate → empty → final
missing-index scan), adds `context.WithTimeout(nonStreamCallTimeout)`,
and forwards `embeddingConfig.Dimension` as the `dimensions` parameter
(Baidu Qianfan v2 uses an OpenAI-compatible API).

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

internal/entity/models/baidu.go

@@ -429,7 +429,7 @@ type baiduEmbeddingResponse struct {
 type baiduEmbeddingData struct {
 	Object    string    `json:"object"`
 	Embedding []float64 `json:"embedding"`
-	Index     int       `json:"index"`
+	Index     *int      `json:"index"`
 }
 
 type baiduUsage struct {
@@ -438,6 +438,12 @@ type baiduUsage struct {
 }
 
 func (b *BaiduModel) Embed(modelName *string, texts []string, apiConfig *APIConfig, embeddingConfig *EmbeddingConfig) ([]EmbeddingData, error) {
+	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")
+	}
 	if len(texts) == 0 {
 		return []EmbeddingData{}, nil
 	}
@@ -453,6 +459,9 @@ func (b *BaiduModel) Embed(modelName *string, texts []string, apiConfig *APIConf
 		"model": *modelName,
 		"input": texts,
 	}
+	if embeddingConfig != nil && embeddingConfig.Dimension > 0 {
+		reqBody["dimensions"] = embeddingConfig.Dimension
+	}
 
 	jsonData, err := json.Marshal(reqBody)
 	if err != nil {
@@ -487,12 +496,37 @@ func (b *BaiduModel) Embed(modelName *string, texts []string, apiConfig *APIConf
 		return nil, fmt.Errorf("failed to parse response: %w", err)
 	}
 
-	var embeddings []EmbeddingData
-	for _, dataElem := range parsed.Data {
-		var embeddingData EmbeddingData
-		embeddingData.Embedding = dataElem.Embedding
-		embeddingData.Index = dataElem.Index
-		embeddings = append(embeddings, embeddingData)
+	if len(parsed.Data) != len(texts) {
+		return nil, fmt.Errorf("expected %d embeddings, got %d", len(texts), len(parsed.Data))
+	}
+
+	embeddings := make([]EmbeddingData, len(texts))
+	seen := make([]bool, len(texts))
+	for _, item := range parsed.Data {
+		if item.Index == nil {
+			return nil, fmt.Errorf("missing index field in embedding item")
+		}
+		idx := *item.Index
+		if idx < 0 || idx >= len(texts) {
+			return nil, fmt.Errorf("embedding index %d out of range", idx)
+		}
+		if seen[idx] {
+			return nil, fmt.Errorf("duplicate embedding index %d", idx)
+		}
+		if len(item.Embedding) == 0 {
+			return nil, fmt.Errorf("empty embedding at index %d", idx)
+		}
+		seen[idx] = true
+		embeddings[idx] = EmbeddingData{
+			Embedding: item.Embedding,
+			Index:     idx,
+		}
+	}
+
+	for i, ok := range seen {
+		if !ok {
+			return nil, fmt.Errorf("missing embedding index %d", i)
+		}
 	}
 
 	return embeddings, nil