feat(aircoding): AirCoding V2 baseline — deterministic multi-agent architecture

Forked from OpenCode v1.17.4 with multi-agent system:
- 5 agents: aircoding, scheduler, worker, architect, reviewer
- Deterministic DAG scheduling engine (coordinator_tick)
- Tool whitelists as hard enforcement
- AirCoding validation plugin
- V1 requirements: C4 docs, ADR, AGENTS.md, debug-log.md
- Design documents in docs/

packages/tui/test/fixture/fixture.ts

@@ -0,0 +1,13 @@
+import { mkdtemp, realpath, rm } from "node:fs/promises"
+import path from "node:path"
+import os from "node:os"
+
+export async function tmpdir() {
+  const directory = await realpath(await mkdtemp(path.join(os.tmpdir(), "opencode-tui-test-")))
+  return {
+    path: directory,
+    async [Symbol.asyncDispose]() {
+      await rm(directory, { recursive: true, force: true })
+    },
+  }
+}