Improve MindSpace visual editor UX and default RMB billing.

Add color-coded edit highlights with an in-preview legend, strip CSP meta
for srcdoc editing, and simplify fullscreen preview to immersive visual edit
only. Default billing to CNY token rates unless H5_USE_BACKEND_COST=1.

Co-authored-by: Cursor <cursoragent@cursor.com>

billing.mjs

@@ -1,5 +1,6 @@
 export function loadBillingConfig() {
-  const useBackendCost = process.env.H5_USE_BACKEND_COST !== '0';
+  // 默认按人民币分（CNY cents）计费；仅当 H5_USE_BACKEND_COST=1 时才用上游 USD 成本换算。
+  const useBackendCost = process.env.H5_USE_BACKEND_COST === '1';
   return {
     useBackendCost,
     usdCnyRate: Number(process.env.H5_USD_CNY_RATE ?? 7.2),
@@ -53,6 +54,8 @@ export function computeDeltaCostCents(previous, current, config = loadBillingCon
     return Math.max(config.minBillCents, Math.ceil(currCost * config.usdCnyRate * 100));
   }
 
+  // 默认路径：按 Token 增量 × 人民币单价（分/1k tokens）扣费。
+
   const prevIn = Number(previous?.lastInputTokens ?? 0);
   const prevOut = Number(previous?.lastOutputTokens ?? 0);
   const deltaIn = Math.max(0, current.accumulatedInputTokens - prevIn);