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

packages/desktop/scripts/prebuild.ts

@@ -0,0 +1,10 @@
+#!/usr/bin/env bun
+import { $ } from "bun"
+
+import { resolveChannel } from "./utils"
+
+const channel = resolveChannel()
+await $`bun ./scripts/copy-icons.ts ${channel}`
+await $`bun ./scripts/copy-metainfo.ts ${channel}`
+
+await $`cd ../opencode && bun script/build-node.ts`