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/core/migration/20260611035744_credential/migration.sql

@@ -0,0 +1,12 @@
+CREATE TABLE `credential` (
+	`id` text PRIMARY KEY,
+	`connector_id` text NOT NULL,
+	`method_id` text NOT NULL,
+	`label` text NOT NULL,
+	`value` text NOT NULL,
+	`active` integer DEFAULT false NOT NULL,
+	`time_created` integer NOT NULL,
+	`time_updated` integer NOT NULL
+);
+--> statement-breakpoint
+CREATE UNIQUE INDEX `credential_connector_active_idx` ON `credential` (`connector_id`) WHERE "credential"."active" = 1;