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/svc/service_context.go

@@ -59,6 +59,7 @@ func NewServiceContext(c config.Config) *ServiceContext {
 	textExtractor := newTextExtractor(c)
 	service := application.NewDesignService(repo, agentRunner, assets, researcher, textExtractor, creativeAgent)
 	service.SetBackgroundRemover(newBackgroundRemover(c))
+	service.SetLayeredDocumentGenerator(newLayeredDocumentGenerator(c))
 	service.SetObjectRecognizer(newObjectRecognizer(c))
 	if mockupAnalyzer, ok := creativeAgent.(design.MockupModelAnalyzer); ok {
 		service.SetMockupModelAnalyzer(mockupAnalyzer)
@@ -317,6 +318,22 @@ func newImageGenerator(c config.Config) piagent.ImageGenerator {
 	return client
 }
 
+func newLayeredDocumentGenerator(c config.Config) design.LayeredDocumentGenerator {
+	opts := c.Agent.Image
+	apiKey := resolveImageAPIKey(opts)
+	client := piagent.NewImageClient(piagent.ImageClientOptions{
+		BaseURL:                      opts.BaseURL,
+		APIKey:                       apiKey,
+		InputImageTransport:          opts.InputImageTransport,
+		TimeoutSeconds:               opts.TimeoutSeconds,
+		ResponseHeaderTimeoutSeconds: opts.ResponseHeaderTimeoutSeconds,
+	})
+	if client == nil {
+		return nil
+	}
+	return client
+}
+
 func newTextExtractor(c config.Config) design.TextExtractor {
 	opts := c.Agent.Text
 	switch opts.Driver {