feat(server): wire quality/count params and layered document generator

Map imageQuality/imageCount and output_format across the HTTP and
WebSocket handlers, pass them into the design service calls, and register
the layered document generator in the service context.

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

server/internal/logic/agent_websocket_logic.go

@@ -57,6 +57,8 @@ type socketStartData struct {
 	EnableWebSearch       bool                `json:"enable_web_search"`
 	ImageModel            string              `json:"image_model"`
 	ImageSize             string              `json:"image_size"`
+	ImageQuality          string              `json:"image_quality"`
+	ImageCount            int                 `json:"image_count"`
 	Mode                  string              `json:"mode"`
 }
 
@@ -177,6 +179,8 @@ func (data socketStartData) toDomainChat(projectID string) design.AgentChatReque
 		EnableWebSearch:       data.EnableWebSearch || hasSocketPreferredToolCategory(data.ToolConfig.PreferToolCategories, "SEARCH"),
 		ImageModel:            data.ImageModel,
 		ImageSize:             data.ImageSize,
+		ImageQuality:          data.ImageQuality,
+		ImageCount:            data.ImageCount,
 		Mode:                  data.Mode,
 	}
 }