Raise Bedrock translator patch coverage

Codecov flagged the PR because the new Bedrock RequestBody branch left one real error path uncovered and one assistant error path that the code could never reach. The user-message image error is now covered directly, and assistant conversion no longer advertises an impossible error return.

Constraint: PR #2237 is blocked by Codecov patch coverage on internal/translator/anthropic_awsbedrock.go

Rejected: Add a synthetic assistant error test | convertAssistantMessage cannot currently fail, so such a test would require artificial production behavior

Confidence: high

Scope-risk: narrow

Directive: Do not reintroduce an error return for assistant conversion unless a real assistant block conversion can fail

Tested: go test ./internal/translator -coverprofile=/tmp/translator.after.cover

Tested: go test ./internal/translator -run 'TestAnthropicToAWSBedrockTranslator_RequestBody_(ToolResultMessages|ToolResultMessagesWithSystemMessages|SingleToolResultNotCoalesced|UnexpectedRole|UserArrayContent|UserArrayContentError|AssistantMessage)' -count=1

Tested: go vet ./internal/translator

Tested: make lint

Not-tested: go test ./... failed locally because port 6060 is occupied by amass, Docker Hub CRD fetch timed out, required e2e Docker image is missing, and Ollama model qwen3:1.7b is unavailable
Signed-off-by: liuhy <liuhongyu@apache.org>

Author: Aias00

internal/translator/anthropic_awsbedrock.go

@@ -97,11 +97,7 @@ func (a *anthropicToAWSBedrockTranslator) RequestBody(_ []byte, body *anthropics
 			}
 			i++
 		case anthropicschema.MessageRoleAssistant:
-			bedrockMsg, convErr := a.convertAssistantMessage(msg)
-			if convErr != nil {
-				return nil, nil, convErr
-			}
-			bedrockReq.Messages = append(bedrockReq.Messages, bedrockMsg)
+			bedrockReq.Messages = append(bedrockReq.Messages, a.convertAssistantMessage(msg))
 			i++
 		default:
 			return nil, nil, fmt.Errorf("%w: unexpected role: %s", internalapi.ErrInvalidRequestBody, msg.Role)
@@ -233,13 +229,13 @@ func (a *anthropicToAWSBedrockTranslator) convertUserMessage(msg *anthropicschem
 	return bedrockMsg, nil
 }
 
-func (a *anthropicToAWSBedrockTranslator) convertAssistantMessage(msg *anthropicschema.MessageParam) (*awsbedrock.Message, error) {
+func (a *anthropicToAWSBedrockTranslator) convertAssistantMessage(msg *anthropicschema.MessageParam) *awsbedrock.Message {
 	bedrockMsg := &awsbedrock.Message{Role: awsbedrock.ConversationRoleAssistant}
 	if msg.Content.Text != "" {
 		bedrockMsg.Content = []*awsbedrock.ContentBlock{
 			{Text: ptr.To(msg.Content.Text)},
 		}
-		return bedrockMsg, nil
+		return bedrockMsg
 	}
 	bedrockMsg.Content = make([]*awsbedrock.ContentBlock, 0, len(msg.Content.Array))
 	for i := range msg.Content.Array {
@@ -274,7 +270,7 @@ func (a *anthropicToAWSBedrockTranslator) convertAssistantMessage(msg *anthropic
 			})
 		}
 	}
-	return bedrockMsg, nil
+	return bedrockMsg
 }
 
 func (a *anthropicToAWSBedrockTranslator) convertToolResultMessage(msg *anthropicschema.MessageParam) *awsbedrock.Message {

internal/translator/anthropic_awsbedrock_test.go

@@ -955,6 +955,39 @@ func TestAnthropicToAWSBedrockTranslator_RequestBody_UserArrayContent(t *testing
 	assert.Equal(t, []string{"END", "STOP"}, bedrockReq.InferenceConfig.StopSequences)
 }
 
+func TestAnthropicToAWSBedrockTranslator_RequestBody_UserArrayContentError(t *testing.T) {
+	translator := NewAnthropicToAWSBedrockTranslator("")
+	req := &anthropicschema.MessagesRequest{
+		Model:     "test-model",
+		MaxTokens: 100,
+		Messages: []anthropicschema.MessageParam{
+			{
+				Role: anthropicschema.MessageRoleUser,
+				Content: anthropicschema.MessageContent{
+					Array: []anthropicschema.ContentBlockParam{
+						{Image: &anthropicschema.ImageBlockParam{
+							Type: "image",
+							Source: anthropicschema.ImageSource{
+								Base64: &anthropicschema.Base64ImageSource{
+									Type:      "base64",
+									MediaType: "application/pdf",
+									Data:      "not-used",
+								},
+							},
+						}},
+					},
+				},
+			},
+		},
+	}
+	rawBody, err := json.Marshal(req)
+	require.NoError(t, err)
+
+	_, _, err = translator.RequestBody(rawBody, req, false)
+	require.Error(t, err)
+	assert.Contains(t, err.Error(), "unsupported image format application/pdf")
+}
+
 func TestAnthropicToAWSBedrockTranslator_RequestBody_ToolResultMessages(t *testing.T) {
 	translator := NewAnthropicToAWSBedrockTranslator("")
 	req := &anthropicschema.MessagesRequest{