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/fixture/plugin.ts

@@ -0,0 +1,10 @@
+import { mkdir } from "fs/promises"
+import path from "path"
+
+export async function markPluginDependenciesReady(dir: string) {
+  await mkdir(path.join(dir, "node_modules"), { recursive: true })
+  await Bun.write(
+    path.join(dir, "package-lock.json"),
+    JSON.stringify({ packages: { "": { dependencies: { "@opencode-ai/plugin": "0.0.0" } } } }),
+  )
+}