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/core/test/model.test.ts

@@ -0,0 +1,23 @@
+import { describe, expect, test } from "bun:test"
+import { Schema } from "effect"
+import { ModelV2 } from "@opencode-ai/core/model"
+import { ProviderV2 } from "@opencode-ai/core/provider"
+
+const decode = Schema.decodeUnknownSync(ModelV2.Ref)
+
+describe("ModelV2.Ref", () => {
+  test("accepts a model selection without a variant", () => {
+    expect(decode({ id: "claude-sonnet", providerID: "anthropic" })).toEqual({
+      id: ModelV2.ID.make("claude-sonnet"),
+      providerID: ProviderV2.ID.make("anthropic"),
+    })
+  })
+
+  test("preserves an explicit model variant", () => {
+    expect(decode({ id: "claude-sonnet", providerID: "anthropic", variant: "high" })).toEqual({
+      id: ModelV2.ID.make("claude-sonnet"),
+      providerID: ProviderV2.ID.make("anthropic"),
+      variant: ModelV2.VariantID.make("high"),
+    })
+  })
+})