Initial commit: img-infinite-canvas AI design workbench MVP

Moteva-style AI design workbench replica. Home prompt creates a project;
the project page provides an infinite canvas with node drag, zoom/pan,
a design chat panel, history replay, image asset upload, and project
save/regenerate.

- Backend: go-zero, DDD layering, sqlc/pgx, optional PostgreSQL; memory
  or Redis cache; asynq job queue; MinIO/S3/R2/OSS object storage;
  sky-valley/pi agent runtime adapter.
- Frontend: Next.js App Router + Vite artifact build, TypeScript, i18n,
  shadcn/ui components, auth (OTP/Turnstile/Google/WeChat).
- Deploy: Docker Compose and k3s manifests.

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

server/internal/infrastructure/piagent/chat_response.go

@@ -0,0 +1,43 @@
+package piagent
+
+import (
+	"encoding/json"
+	"strings"
+)
+
+func trimErrorBody(body []byte) string {
+	value := strings.TrimSpace(string(body))
+	if value == "" {
+		return "empty error body"
+	}
+	if len(value) > 1200 {
+		return value[:1200]
+	}
+	return value
+}
+
+func decodeChatContent(raw json.RawMessage) string {
+	var text string
+	if err := json.Unmarshal(raw, &text); err == nil {
+		return text
+	}
+
+	var parts []struct {
+		Type string `json:"type"`
+		Text string `json:"text"`
+	}
+	if err := json.Unmarshal(raw, &parts); err == nil {
+		var builder strings.Builder
+		for _, part := range parts {
+			if strings.TrimSpace(part.Text) == "" {
+				continue
+			}
+			if builder.Len() > 0 {
+				builder.WriteString("\n")
+			}
+			builder.WriteString(part.Text)
+		}
+		return builder.String()
+	}
+	return string(raw)
+}