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
- System prompt injection for routing
- V1 requirements: C4 docs, ADR, AGENTS.md, debug-log.md
- Design documents in docs/

packages/opencode/test/lib/filesystem.ts

@@ -0,0 +1,10 @@
+import path from "path"
+import { Effect, FileSystem } from "effect"
+
+export const writeFileStringScoped = Effect.fn("test.writeFileStringScoped")(function* (file: string, text: string) {
+  const fs = yield* FileSystem.FileSystem
+  yield* fs.makeDirectory(path.dirname(file), { recursive: true })
+  yield* fs.writeFileString(file, text)
+  yield* Effect.addFinalizer(() => fs.remove(file, { force: true }).pipe(Effect.orDie))
+  return file
+})