fix(cli): protect existing Windows Codex shims

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

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

src/cli/install-codex/codex-cache.test.ts

@@ -1,3 +1,6 @@
+/// <reference path="../../../bun-test.d.ts" />
+/// <reference types="bun-types" />
+
 import { describe, expect, test } from "bun:test"
 import { mkdir, mkdtemp, readFile, readlink, writeFile } from "node:fs/promises"
 import { tmpdir } from "node:os"
@@ -35,8 +38,8 @@ describe("codex-cache", () => {
     await writeFile(join(pluginRoot, "dist", "cli.js"), "#!/usr/bin/env node\n")
 
     // when
-    const first = await linkCachedPluginBins({ binDir, pluginRoot })
-    const second = await linkCachedPluginBins({ binDir, pluginRoot })
+    const first = await linkCachedPluginBins({ binDir, pluginRoot, platform: "linux" })
+    const second = await linkCachedPluginBins({ binDir, pluginRoot, platform: "linux" })
 
     // then
     expect(first).toHaveLength(1)
@@ -64,4 +67,29 @@ describe("codex-cache", () => {
     expect(commandShim).toContain("@echo off")
     expect(commandShim).toContain(`node "${join(pluginRoot, "dist", "cli.js")}" %*`)
   })
+
+  test("rejects existing non-generated Windows command shims", async () => {
+    // given
+    const root = await mkdtemp(join(tmpdir(), "omo-codex-cache-"))
+    const pluginRoot = join(root, "plugin")
+    const binDir = join(root, "bin")
+    await mkdir(pluginRoot, { recursive: true })
+    await mkdir(binDir, { recursive: true })
+    await writeFile(join(pluginRoot, "package.json"), JSON.stringify({ name: "@scope/omo", bin: { "omo-hook": "dist/cli.js" } }))
+    await mkdir(join(pluginRoot, "dist"), { recursive: true })
+    await writeFile(join(pluginRoot, "dist", "cli.js"), "#!/usr/bin/env node\n")
+    await writeFile(join(binDir, "omo-hook.cmd"), "@echo off\r\necho custom\r\n")
+
+    // when
+    let rejected = false
+    try {
+      await linkCachedPluginBins({ binDir, pluginRoot, platform: "win32" })
+    } catch (error) {
+      rejected = error instanceof Error && error.message.includes("already exists and is not a generated command shim")
+    }
+
+    // then
+    expect(rejected).toBe(true)
+    expect(await readFile(join(binDir, "omo-hook.cmd"), "utf8")).toContain("echo custom")
+  })
 })

src/cli/install-codex/codex-cache.ts

@@ -4,6 +4,8 @@ import type { InstalledPlugin, RunCommand } from "./types"
 
 type LinkPlatform = NodeJS.Platform
 
+const COMMAND_SHIM_MARKER = ":: generated by oh-my-openagent Codex installer"
+
 export async function installCachedPlugin(input: {
   readonly codexHome: string
   readonly marketplaceName: string
@@ -163,13 +165,16 @@ async function replaceSymlink(linkPath: string, targetPath: string): Promise<voi
 
 async function replaceCommandShim(linkPath: string, targetPath: string): Promise<void> {
   if (await existingNonShim(linkPath)) throw new Error(`${linkPath} already exists and is not a command shim`)
-  await writeFile(linkPath, `@echo off\r\nnode "${targetPath}" %*\r\n`)
+  await writeFile(linkPath, `@echo off\r\n${COMMAND_SHIM_MARKER}\r\nnode "${targetPath}" %*\r\n`)
 }
 
 async function existingNonShim(path: string): Promise<boolean> {
   try {
     const stat = await lstat(path)
-    return !stat.isFile()
+    if (!stat.isFile()) return true
+    const content = await readFile(path, "utf8")
+    if (content.includes(COMMAND_SHIM_MARKER)) return false
+    throw new Error(`${path} already exists and is not a generated command shim`)
   } catch (error) {
     if (isNodeErrorWithCode(error) && error.code === "ENOENT") return false
     throw error