refactor(provider): return canonical auth methods

Make the provider auth service own the canonical Methods DTO and align the server test cleanup pattern with the other HttpApi slices.

packages/opencode/test/server/provider-httpapi-auth.test.ts

@@ -1,12 +1,17 @@
-import { describe, expect, test } from "bun:test"
+import { afterEach, describe, expect, test } from "bun:test"
 import path from "path"
 import fs from "fs/promises"
+import { Instance } from "../../src/project/instance"
 import { Server } from "../../src/server/server"
 import { tmpdir } from "../fixture/fixture"
 import { Log } from "../../src/util/log"
 
 Log.init({ print: false })
 
+afterEach(async () => {
+  await Instance.disposeAll()
+})
+
 describe("experimental provider httpapi", () => {
   test("lists provider auth methods and serves docs", async () => {
     await using tmp = await tmpdir({