Replace Instance.disposeAll/load with fixture helper (#25418)

packages/opencode/test/server/httpapi-instance.legacy.test.ts

@@ -6,7 +6,7 @@ import { Server } from "../../src/server/server"
 import { InstancePaths } from "../../src/server/routes/instance/httpapi/groups/instance"
 import * as Log from "@opencode-ai/core/util/log"
 import { resetDatabase } from "../fixture/db"
-import { tmpdir } from "../fixture/fixture"
+import { disposeAllInstances, tmpdir } from "../fixture/fixture"
 
 void Log.init({ print: false })
 
@@ -37,7 +37,7 @@ async function waitDisposed(directory: string) {
 
 afterEach(async () => {
   Flag.OPENCODE_EXPERIMENTAL_HTTPAPI = original
-  await Instance.disposeAll()
+  await disposeAllInstances()
   await resetDatabase()
 })