fix: plugin shortcut support

[edmundhung]

Fix #21166

I am terribly sorry having to come back to this the 3rd time. My previous attempt resolves the server restart issue only when no plugin defines their own shortcut using server.bindCliShortcuts().

When a plugin defines its own custom shortcut (e.g. x + enter), it works fine when the dev server is just started:

> pnpm run dev

> vite-plugin-shortcut-issue@0.0.0 dev /Users/edmund/Workspace/vite-plugin-shortcut-issue
> vite


  VITE v7.2.6  ready in 89 ms

  ➜  Local:   http://localhost:5173/
  ➜  Network: use --host to expose
  ➜  press h + enter to show help
h

  Shortcuts
  press x + enter to log a message to the console
  press r + enter to restart the server
  press u + enter to show server url
  press o + enter to open in browser
  press c + enter to clear console
  press q + enter to quit
x
Hello World

However, if you change the shortcut message to Hello updated server defined in the config file and save it, the server restarts and this happens:

12:28:41 [vite] vite.config.ts changed, restarting server...
12:28:41 [vite] server restarted.
x
Hello updated server
Hello World

Here is a reproduction: https://github.com/edmundhung/vite-plugin-shortcut-issue

The issue here is when restartServer() creates a new server and the plugin calls server.bindCLIShortcuts(), a readline interface is also created. It gets detached because of my changes in #21166:

vite/packages/vite/src/node/server/index.ts

Lines 1254 to 1255 in 5d2c31f

	// Ensure the new server has no stale readline reference
	newServer._rl = undefined

Another readline interface then get created with the stale shortcut options (the one that logs Hello World instead of the updated Hello updated server message) in

vite/packages/vite/src/node/server/index.ts

Lines 1280 to 1288 in 5d2c31f

	if (shortcutsOptions) {
	shortcutsOptions.print = false
	bindCLIShortcuts(
	server,
	shortcutsOptions,
	// Skip environment checks since shortcuts were bound before restart
	true,
	)
	}

Initially, I tried detaching the server._rl instance instead so we preserve the new readline instance created in the plugin:

-newServer._rl = undefined
+server._rl = undefined

But it runs into another issue: closing a readline interface on process.stdin causes already opened readline interfaces to stop receiving input.

This PR:

1. Preserves the readline interface (_rl) across server restart (avoids issues when closing/reopening readline)
2. Transfers _shortcutsOptions to the new server so plugin shortcuts can be properly merged when plugin register custom shortcut
3. Maintains shortcut order (manually bound shortcuts stay above plugin shortcuts)

[sapphi-red]

Thanks! I've pushed a commit to simplify the state handling a bit.