refactor(core): convert opencode tests to nodes (#34453)

packages/core/src/observability.ts

@@ -1,6 +1,7 @@
 export * as Observability from "./observability"
 
 import { NodeFileSystem } from "@effect/platform-node"
+import { LayerNode } from "./effect/layer-node"
 import { Effect, Layer, Logger, References } from "effect"
 import { FetchHttpClient } from "effect/unstable/http"
 import { OtlpSerialization } from "effect/unstable/observability"
@@ -19,3 +20,5 @@ export const layer = Layer.unwrap(
     return Layer.merge(logs, yield* Effect.promise(Otlp.tracingLayer))
   }),
 )
+
+export const node = LayerNode.make({ name: "observability", layer, deps: [] })