Fix(Go): make OpenRouter Encode fail loudly on malformed responses (#14717)

### What problem does this PR solve?

The OpenRouter `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.
There were three concrete gaps:

- No count-mismatch check between `data` length and input texts (only
checked for empty)
- No duplicate-index detection (a duplicate would silently overwrite)
- Parse failures on individual items returned partial slices instead of
erroring

This PR replaces `map[string]interface{}` parsing with a typed
`openrouterEmbeddingResponse` struct and applies the same 3-layer
validation used in the other drivers (count mismatch → out-of-range
index → duplicate index), so any malformed response produces a clear
error instead of corrupted data.

### Type of change

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

internal/entity/models/openrouter.go

@@ -351,10 +351,20 @@ func (o *OpenRouterModel) ChatStreamlyWithSender(modelName string, messages []Me
 	return scanner.Err()
 }
 
+type openrouterEmbeddingResponse struct {
+	Data []struct {
+		Index     int       `json:"index"`
+		Embedding []float64 `json:"embedding"`
+	} `json:"data"`
+}
+
 func (o *OpenRouterModel) Encode(modelName *string, texts []string, apiConfig *APIConfig, embeddingConfig *EmbeddingConfig) ([][]float64, error) {
 	if len(texts) == 0 {
 		return [][]float64{}, nil
 	}
+	if modelName == nil || *modelName == "" {
+		return nil, fmt.Errorf("model name is required")
+	}
 
 	var region = "default"
 	if apiConfig != nil && apiConfig.Region != nil && *apiConfig.Region != "" {
@@ -368,6 +378,10 @@ func (o *OpenRouterModel) Encode(modelName *string, texts []string, apiConfig *A
 		"input": texts,
 	}
 
+	if embeddingConfig != nil && embeddingConfig.Dimension > 0 {
+		reqBody["dimensions"] = embeddingConfig.Dimension
+	}
+
 	jsonData, err := json.Marshal(reqBody)
 	if err != nil {
 		return nil, fmt.Errorf("failed to marshal request: %w", err)
@@ -398,52 +412,26 @@ func (o *OpenRouterModel) Encode(modelName *string, texts []string, apiConfig *A
 		return nil, fmt.Errorf("OpenRouter embedding API error: status %d, body: %s", resp.StatusCode, string(body))
 	}
 
-	var result map[string]interface{}
+	var result openrouterEmbeddingResponse
 	if err = json.Unmarshal(body, &result); err != nil {
 		return nil, fmt.Errorf("failed to decode response: %w", err)
 	}
 
-	dataObj, ok := result["data"].([]interface{})
-	if !ok || len(dataObj) == 0 {
-		return nil, fmt.Errorf("OpenRouter embedding response contains no data: %s", string(body))
+	if len(result.Data) != len(texts) {
+		return nil, fmt.Errorf("expected %d embeddings, got %d", len(texts), len(result.Data))
 	}
 
 	embeddings := make([][]float64, len(texts))
-
-	for _, item := range dataObj {
-		dataMap, ok := item.(map[string]interface{})
-		if !ok {
-			continue
+	seen := make([]bool, len(texts))
+	for _, item := range result.Data {
+		if item.Index < 0 || item.Index >= len(texts) {
+			return nil, fmt.Errorf("embedding index %d out of range", item.Index)
 		}
-
-		indexFloat, ok := dataMap["index"].(float64)
-		if !ok {
-			continue
+		if seen[item.Index] {
+			return nil, fmt.Errorf("duplicate embedding index %d", item.Index)
 		}
-		index := int(indexFloat)
-
-		if index < 0 || index >= len(texts) {
-			continue
-		}
-
-		embeddingSlice, ok := dataMap["embedding"].([]interface{})
-		if !ok {
-			continue
-		}
-
-		embedding := make([]float64, len(embeddingSlice))
-		for j, v := range embeddingSlice {
-			switch val := v.(type) {
-			case float64:
-				embedding[j] = val
-			case float32:
-				embedding[j] = float64(val)
-			default:
-				return nil, fmt.Errorf("unexpected embedding value type")
-			}
-		}
-
-		embeddings[index] = embedding
+		seen[item.Index] = true
+		embeddings[item.Index] = item.Embedding
 	}
 
 	return embeddings, nil