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/opencode/test/fixture/flag.ts

@@ -0,0 +1,20 @@
+import type { WorkspaceV2 } from "@opencode-ai/core/workspace"
+import { Flag } from "@opencode-ai/core/flag/flag"
+import { Effect, Scope } from "effect"
+
+/**
+ * Scoped override for `Flag.OPENCODE_WORKSPACE_ID`. Saves the previous value
+ * on entry and restores it via finalizer when the surrounding scope closes —
+ * preserves the original try/finally semantics regardless of test outcome.
+ */
+export function withFixedWorkspaceID(id: WorkspaceV2.ID): Effect.Effect<void, never, Scope.Scope> {
+  return Effect.gen(function* () {
+    const previous = Flag.OPENCODE_WORKSPACE_ID
+    Flag.OPENCODE_WORKSPACE_ID = id
+    yield* Effect.addFinalizer(() =>
+      Effect.sync(() => {
+        Flag.OPENCODE_WORKSPACE_ID = previous
+      }),
+    )
+  })
+}