fix(browser): fix base for client script

[hi-ogawa]

Description

• closes browser: @vite/client cannot load when a custom base is set #6509

Browser mode's vite server forces base: "/", but injected client script was using a base from the original config server.project.config.base.

vitest/packages/browser/src/node/index.ts

Line 29 in 54a066d

const server = new BrowserServer(project, '/')

vitest/packages/browser/src/node/index.ts

Lines 37 to 39 in 155b690

	const vite = await createViteServer({
	...project.options, // spread project config inlined in root workspace config
	base: '/',

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