feat(composer): carry reference image names and submit on Enter

Propagate an optional imageName through the agent content pipeline
(frontend types → API → domain → prompt building) so reference images
render with their name instead of a bare "image" label.

Also switch PromptComposer to submit on plain Enter (Shift+Enter for
newline, IME-safe) and add a submitDisabled guard wired from the canvas
and home composers.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

server/img_infinite_canvas.api

@@ -369,6 +369,7 @@ type AgentContent {
 	Text        string `json:"text,optional"`
 	TextSource  string `json:"textSource,optional"`
 	ImageUrl    string `json:"imageUrl,optional"`
+	ImageName   string `json:"imageName,optional"`
 	ImageWidth  int64  `json:"imageWidth,optional"`
 	ImageHeight int64  `json:"imageHeight,optional"`
 }

server/internal/application/design_service.go

@@ -4510,7 +4510,13 @@ func promptFromAgentMessages(messages []design.AgentChatMessage) string {
 					if builder.Len() > 0 {
 						builder.WriteString("\n")
 					}
-					builder.WriteString("Reference image: ")
+					builder.WriteString("Reference image")
+					if imageName := strings.TrimSpace(content.ImageName); imageName != "" {
+						builder.WriteString(" (")
+						builder.WriteString(compactReferenceImageName(imageName))
+						builder.WriteString(")")
+					}
+					builder.WriteString(": ")
 					builder.WriteString(imageURL)
 				}
 			}
@@ -4519,6 +4525,10 @@ func promptFromAgentMessages(messages []design.AgentChatMessage) string {
 	return builder.String()
 }
 
+func compactReferenceImageName(value string) string {
+	return strings.Join(strings.Fields(value), " ")
+}
+
 func hasUserPromptTextInAgentMessages(messages []design.AgentChatMessage) bool {
 	for _, message := range messages {
 		if strings.TrimSpace(message.Role) != "" && strings.ToLower(strings.TrimSpace(message.Role)) != "user" {

server/internal/domain/design/agent.go

@@ -18,6 +18,7 @@ type AgentContent struct {
 	Text        string
 	TextSource  string
 	ImageURL    string
+	ImageName   string
 	ImageWidth  int64
 	ImageHeight int64
 }

server/internal/logic/agent_websocket_logic.go

@@ -70,6 +70,7 @@ type socketContent struct {
 	Text        string `json:"text"`
 	TextSource  string `json:"text_source"`
 	ImageURL    string `json:"image_url"`
+	ImageName   string `json:"image_name"`
 	ImageWidth  int64  `json:"image_width"`
 	ImageHeight int64  `json:"image_height"`
 }
@@ -155,6 +156,7 @@ func (data socketStartData) toDomainChat(projectID string) design.AgentChatReque
 				Text:        content.Text,
 				TextSource:  content.TextSource,
 				ImageURL:    content.ImageURL,
+				ImageName:   content.ImageName,
 				ImageWidth:  content.ImageWidth,
 				ImageHeight: content.ImageHeight,
 			})

server/internal/logic/mapper.go

@@ -519,6 +519,7 @@ func toDomainAgentChat(req *types.AgentChatRequest) design.AgentChatRequest {
 				Text:        content.Text,
 				TextSource:  content.TextSource,
 				ImageURL:    content.ImageUrl,
+				ImageName:   content.ImageName,
 				ImageWidth:  content.ImageWidth,
 				ImageHeight: content.ImageHeight,
 			})

server/internal/types/types.go

@@ -49,6 +49,7 @@ type AgentContent struct {
 	Text        string `json:"text,optional"`
 	TextSource  string `json:"textSource,optional"`
 	ImageUrl    string `json:"imageUrl,optional"`
+	ImageName   string `json:"imageName,optional"`
 	ImageWidth  int64  `json:"imageWidth,optional"`
 	ImageHeight int64  `json:"imageHeight,optional"`
 }