fix: add cjk fallback fonts for psd export

lib/agents/psd-template-renderer.ts

@@ -136,6 +136,47 @@ function getFontMimeType(font: AgentPsdFont | undefined, fontFamily: string) {
   return "font/ttf";
 }
 
+const GENERIC_FONT_FAMILIES = new Set(["sans-serif", "serif", "monospace", "cursive", "fantasy", "system-ui"]);
+const CJK_FALLBACK_FONT_FAMILIES = [
+  "Noto Sans CJK SC",
+  "Noto Sans SC",
+  "Source Han Sans SC",
+  "Microsoft YaHei",
+  "PingFang SC",
+  "Hiragino Sans GB",
+  "WenQuanYi Zen Hei",
+  "SimHei",
+  "Arial Unicode MS",
+  "sans-serif",
+] as const;
+
+function textContainsCjkGlyphs(value: string) {
+  return /[\u3400-\u9fff\u3040-\u30ff\uac00-\ud7af]/.test(String(value || ""));
+}
+
+function buildSvgFontFamilyStack(fontFamily: string, text: string) {
+  const familyTokens = new Set<string>();
+  const primaryFamily = String(fontFamily || "").trim();
+
+  if (primaryFamily) {
+    familyTokens.add(primaryFamily);
+  }
+
+  if (textContainsCjkGlyphs(text)) {
+    for (const fallbackFamily of CJK_FALLBACK_FONT_FAMILIES) {
+      familyTokens.add(fallbackFamily);
+    }
+  } else {
+    familyTokens.add("sans-serif");
+  }
+
+  return Array.from(familyTokens)
+    .map((family) =>
+      GENERIC_FONT_FAMILIES.has(family) ? family : `"${escapeXml(family)}"`
+    )
+    .join(", ");
+}
+
 async function createTextOverlayBuffer(params: {
   width: number;
   height: number;
@@ -192,6 +233,7 @@ async function createTextOverlayBuffer(params: {
   }
 
   const escapedFamily = escapeXml(fontFamily || "sans-serif");
+  const fontFamilyStack = buildSvgFontFamilyStack(fontFamily, normalizedText);
   const fontFaceCss = fontBuffer
     ? `@font-face { font-family: "${escapedFamily}"; src: url("data:${getFontMimeType(font, fontFamily)};base64,${fontBuffer.toString("base64")}"); }`
     : "";
@@ -217,7 +259,7 @@ async function createTextOverlayBuffer(params: {
       <defs>
         <style>
           ${fontFaceCss}
-          .text { font-family: "${escapedFamily}", sans-serif; font-size: ${adjustedFontSize}px; font-weight: ${fontWeight}; fill: ${textColor}; letter-spacing: ${letterSpacing}px; }
+          .text { font-family: ${fontFamilyStack}; font-size: ${adjustedFontSize}px; font-weight: ${fontWeight}; fill: ${textColor}; letter-spacing: ${letterSpacing}px; }
         </style>
         <clipPath id="${clipId}">
           <rect x="0" y="0" width="${width}" height="${height}" />