feat(core): flatten provider config and load native packages (#35563)

Co-authored-by: Dax Raad <d@ironbay.co>

packages/core/test/config/model.test.ts

@@ -0,0 +1,28 @@
+import { describe, expect, test } from "bun:test"
+import { ConfigModel } from "@opencode-ai/core/config/model"
+import { Model } from "@opencode-ai/schema/model"
+import { Provider } from "@opencode-ai/schema/provider"
+import { Schema } from "effect"
+
+const decode = Schema.decodeUnknownSync(ConfigModel.Selection)
+
+describe("ConfigModel.Selection", () => {
+  test("normalizes short and explicit model selections", () => {
+    expect(decode("openrouter/openai/gpt-5#high")).toEqual({
+      providerID: Provider.ID.make("openrouter"),
+      model: Model.ID.make("openai/gpt-5"),
+      variant: Model.VariantID.make("high"),
+    })
+    expect(decode({ providerID: "anthropic", model: "claude-sonnet", variant: "high" })).toEqual({
+      providerID: Provider.ID.make("anthropic"),
+      model: Model.ID.make("claude-sonnet"),
+      variant: Model.VariantID.make("high"),
+    })
+  })
+
+  test("rejects malformed selections and reserved fragments", () => {
+    expect(() => decode("gpt-5")).toThrow()
+    expect(() => decode("openai/gpt-5#")).toThrow()
+    expect(() => decode({ providerID: "openai", model: "gpt-5#high" })).toThrow()
+  })
+})