test(file): dispose instances after httpapi test

Align the file HttpApi server test with the shared instance cleanup pattern used by the other experimental slices.

packages/opencode/test/server/file-httpapi.test.ts

@@ -1,11 +1,16 @@
-import { describe, expect, test } from "bun:test"
+import { afterEach, describe, expect, test } from "bun:test"
 import path from "path"
+import { Instance } from "../../src/project/instance"
 import { Server } from "../../src/server/server"
 import { Log } from "../../src/util/log"
 import { tmpdir } from "../fixture/fixture"
 
 Log.init({ print: false })
 
+afterEach(async () => {
+  await Instance.disposeAll()
+})
+
 describe("experimental file httpapi", () => {
   test("lists files, reads content, reports status, and serves docs", async () => {
     await using tmp = await tmpdir({