fix: avoid base string coercion in auto-reply formatting

src/auto-reply/templating.ts

@@ -78,11 +78,32 @@ export type TemplateContext = MsgContext & {
   IsNewSession?: string;
 };
 
+function formatTemplateValue(value: unknown): string {
+  if (value == null) return "";
+  if (typeof value === "string") return value;
+  if (typeof value === "number" || typeof value === "boolean" || typeof value === "bigint") {
+    return String(value);
+  }
+  if (Array.isArray(value)) {
+    return value
+      .flatMap((entry) => {
+        if (entry == null) return [];
+        if (typeof entry === "string") return [entry];
+        if (typeof entry === "number" || typeof entry === "boolean" || typeof entry === "bigint") {
+          return [String(entry)];
+        }
+        return [];
+      })
+      .join(",");
+  }
+  return "";
+}
+
 // Simple {{Placeholder}} interpolation using inbound message context.
 export function applyTemplate(str: string | undefined, ctx: TemplateContext) {
   if (!str) return "";
   return str.replace(/{{\s*(\w+)\s*}}/g, (_, key) => {
     const value = ctx[key as keyof TemplateContext];
-    return value == null ? "" : String(value);
+    return formatTemplateValue(value);
   });
 }