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/util/error.test.ts

@@ -0,0 +1,16 @@
+import { describe, expect, test } from "bun:test"
+import { NamedError } from "@opencode-ai/core/util/error"
+import { MessageError } from "../../src/session/message-error"
+
+describe("util.error", () => {
+  test("schema-backed named errors are real NamedError instances", () => {
+    const error = new MessageError.AuthError({ providerID: "anthropic", message: "boom" })
+
+    expect(error).toBeInstanceOf(NamedError)
+    expect(error.toObject()).toEqual({ name: "ProviderAuthError", data: { providerID: "anthropic", message: "boom" } })
+  })
+
+  test("named errors without fields serialize data", () => {
+    expect(new MessageError.OutputLengthError({}).toObject()).toEqual({ name: "MessageOutputLengthError", data: {} })
+  })
+})