feat(simulation): add driver controlled backend LLM (#35186)

packages/server/src/routes.ts

@@ -72,7 +72,7 @@ function makeRoutes<AuthError, AuthServices>(
   const serviceLayer = simulationEnabled()
     ? Layer.unwrap(
         Effect.gen(function* () {
-          const { simulationReplacements } = yield* Effect.promise(() => import("./simulation"))
+          const { simulationReplacements } = yield* Effect.promise(() => import("@opencode-ai/simulation/backend"))
           return AppNodeBuilder.build(applicationServices, [...replacements, ...simulationReplacements])
         }),
       )

packages/server/src/simulation/index.ts

@@ -1,14 +0,0 @@
-import { LayerNode } from "@opencode-ai/core/effect/layer-node"
-
-/**
- * Layer replacements applied when the server is built in simulation mode.
- *
- * Empty for now; simulation-mode implementations will populate this with
- * replacement nodes/layers that swap real services for simulated ones (e.g.
- * a fake filesystem). The server merges these into the app node build when
- * `OPENCODE_SIMULATION` is enabled, via a dynamic import so this module is
- * never loaded eagerly.
- */
-export const simulationReplacements: LayerNode.Replacements = []
-
-export * as Simulation from "./index"