test(lsp): use named tmpdir import to avoid node:os mock leak

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/tools/lsp/utils.test.ts

@@ -1,14 +1,14 @@
 import { describe, expect, it } from "bun:test"
 import { mkdirSync, mkdtempSync, rmSync, writeFileSync } from "fs"
+import { tmpdir } from "os"
 import { join } from "path"
-import os from "os"
 
 import { findWorkspaceRoot } from "./lsp-client-wrapper"
 
 describe("lsp utils", () => {
   describe("findWorkspaceRoot", () => {
     it("returns an existing directory even when the file path points to a non-existent nested path", () => {
-      const tmp = mkdtempSync(join(os.tmpdir(), "omo-lsp-root-"))
+      const tmp = mkdtempSync(join(tmpdir(), "omo-lsp-root-"))
       try {
         // Add a marker so the function can discover the workspace root.
         writeFileSync(join(tmp, "package.json"), "{}")
@@ -23,7 +23,7 @@ describe("lsp utils", () => {
     })
 
     it("prefers the nearest marker directory when markers exist above the file", () => {
-      const tmp = mkdtempSync(join(os.tmpdir(), "omo-lsp-marker-"))
+      const tmp = mkdtempSync(join(tmpdir(), "omo-lsp-marker-"))
       try {
         const repo = join(tmp, "repo")
         const src = join(repo, "src")