feat: 品牌替换 + 启动优化 + AGENTS.md 模板定制

- 品牌替换：OpenCode/opencode → AirCoding/aircoding（16+ 文件）
- Logo ASCII art：修复 left/right 行数不匹配导致的启动崩溃
- 启动诊断：添加 OPENCODE_PRINT_TIMING 计时探针
- dev 模式默认 --pure 跳过外部插件加载
- AGENTS.md 模板：追加 AirCoding 多 Agent 专项段落
- architect prompt + plugin：强化 AGENTS.md 产出验证

infra/stage.ts

@@ -0,0 +1,21 @@
+export const domain = (() => {
+  if ($app.stage === "production") return "opencode.ai"
+  if ($app.stage === "dev") return "dev.opencode.ai"
+  return `${$app.stage}.dev.opencode.ai`
+})()
+
+export const zoneID = "430ba34c138cfb5360826c4909f99be8"
+export const awsStage = $app.stage === "production" ? "production" : "dev"
+export const deployAws = $app.stage === awsStage
+
+new cloudflare.RegionalHostname("RegionalHostname", {
+  hostname: domain,
+  regionKey: "us",
+  zoneId: zoneID,
+})
+
+export const shortDomain = (() => {
+  if ($app.stage === "production") return "opncd.ai"
+  if ($app.stage === "dev") return "dev.opncd.ai"
+  return `${$app.stage}.dev.opncd.ai`
+})()