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

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

packages/core/test/plugin/fixtures/variant-source-plugin.ts

@@ -1,4 +1,5 @@
 import { define } from "@opencode-ai/plugin/v2/effect"
+import { ProviderV2 } from "@opencode-ai/core/provider"
 import { Effect } from "effect"
 
 export default define({
@@ -7,14 +8,11 @@ export default define({
     ctx.catalog
       .transform((catalog) => {
         catalog.provider.update("configured", (provider) => {
-          provider.api = { type: "aisdk", package: "@ai-sdk/openai-compatible" }
+          provider.package = ProviderV2.aisdk("@ai-sdk/openai-compatible")
         })
         catalog.model.update("configured", "glm-5.2", (model) => {
-          model.api = {
-            id: "glm-5.2",
-            type: "aisdk",
-            package: "@ai-sdk/openai-compatible",
-          }
+          model.modelID = "glm-5.2"
+          model.package = ProviderV2.aisdk("@ai-sdk/openai-compatible")
           model.variants = [
             {
               id: "high",