fix(optimize-deps): ignore ERR_CLOSED_SERVER in scanner

[sapphi-red]

This PR tries to fix flaky failures like https://github.com/vitejs/vite/actions/runs/28230863726/job/83634064856#step:11:165:

[plugin vite:dep-scan:resolve]
Error: The server is being restarted or closed. Request is outdated
    at throwClosedServerError (D:/a/vite/vite/packages/vite/src/node/server/pluginContainer.ts:129:20)
    at EnvironmentPluginContainer.resolveId (D:/a/vite/vite/packages/vite/src/node/server/pluginContainer.ts:395:9)
    at resolveId (D:/a/vite/vite/packages/vite/src/node/optimizer/scan.ts:362:40)
    at resolve (D:/a/vite/vite/packages/vite/src/node/optimizer/scan.ts:381:28)
    at PluginContextImpl.resolveId (D:/a/vite/vite/packages/vite/src/node/optimizer/scan.ts:616:34)
    at plugin (file:///D:/a/vite/vite/node_modules/.pnpm/rolldown@1.1.3/node_modules/rolldown/dist/shared/bindingify-input-options-CzVhGygm.mjs:1420:30)
    at plugin.<computed> (file:///D:/a/vite/vite/node_modules/.pnpm/rolldown@1.1.3/node_modules/rolldown/dist/shared/bindingify-input-options-CzVhGygm.mjs:1961:18)

⎯⎯⎯⎯⎯⎯ Unhandled Errors ⎯⎯⎯⎯⎯⎯

Vitest caught 1 unhandled error during the test run.
This might cause false positive tests. Resolve unhandled errors to make sure your tests are not affected.

⎯⎯⎯⎯⎯⎯ Unhandled Error ⎯⎯⎯⎯⎯⎯⎯
Error: [vitest-pool]: Worker forks emitted error.
 ❯ EventEmitter.onTaskError node_modules/.pnpm/vitest@4.1.9_@types+node@24.13.2_vite@packages+vite/node_modules/vitest/dist/chunks/cli-api.24X8XwN1.js:3459:21
 ❯ EventEmitter.emit node:events:509:28
 ❯ ChildProcess.emitUnexpectedExit node_modules/.pnpm/vitest@4.1.9_@types+node@24.13.2_vite@packages+vite/node_modules/vitest/dist/chunks/cli-api.24X8XwN1.js:3025:22
 ❯ ChildProcess.emit node:events:509:28
 ❯ Process.ChildProcess._handle.onexit node:internal/child_process:295:12

Caused by: Error: Worker exited unexpectedly
 ❯ ChildProcess.emitUnexpectedExit node_modules/.pnpm/vitest@4.1.9_@types+node@24.13.2_vite@packages+vite/node_modules/vitest/dist/chunks/cli-api.24X8XwN1.js:3023:33
 ❯ ChildProcess.emit node:events:509:28
 ❯ Process.ChildProcess._handle.onexit node:internal/child_process:295:12

The background dependency scanner resolves through the dev plugin container, and when a test tears down the server mid-scan, resolveId throws ERR_CLOSED_SERVER, rejecting the scan on a promise chain nothing awaits. This triggers an unhandled rejection that crashes the vitest worker even though all assertions passed.