Write binary files given to ready() as bytes in both Workers #65

Current implementation

Reviewed at 750be3a.

• VrowzerConfig.files is Record<string, string | ArrayBuffer>. Its documentation says that a value "can be either a string or an ArrayBuffer".
• initialize() spreads config.files into allFiles as Record<string, string> and sends allFiles to both Workers:
  • to the Web Worker, as V_WW_SETUP's files;
  • to the Service Worker, as V_FS_INIT's text field files. The binary field binaryFiles is not used.
• The Web Worker writes these files through setupVirtualFiles(), updateFiles() and updateFile(), with fs.writeFileSync(path, content, { encoding: 'utf8' }) (setupVirtualFiles(), updateFile()).
• The Service Worker's subscriber writes V_FS_INIT.files as text, with writeToVol(path, 'text', content). Its binaryFiles branch writes bytes correctly, but the runtime does not use it.

Verification

I ran the following with Node.js v24.21.0. It used the built @vrowzer/fs (packages/fs/dist), built from ba60d7b. @vrowzer/fs is unchanged in 750be3a.

const subscriber = createFileSystemSubscriber(fs)
const bytes = [0x89, 0x50, 0x4e, 0x47, 0x00, 0xff, 0x10]

// What the runtime sends to the Service Worker for ready({ files })
subscriber.handleMessage({ type: 'V_FS_INIT', files: { '/public/init.png': new Uint8Array(bytes).buffer } })
;[...fs.readFileSync('/public/init.png')]
// [91, 111, 98, 106, 101, 99, 116, 32, 65, 114, 114, 97, 121, 66, 117, 102, 102, 101, 114, 93]
// = "[object ArrayBuffer]"

// What addFile() sends
subscriber.handleMessage({ type: 'V_FS_WRITE', path: '/public/write.png', encoding: 'binary', content: new Uint8Array(bytes).buffer })
;[...fs.readFileSync('/public/write.png')]
// [137, 80, 78, 71, 0, 255, 16]

Requested behavior

• Binary files given to ready() are written as bytes in both Workers.
• The caller's ArrayBuffers stay usable. Each Worker gets its own copy, as addFile() does since #61.
• Text files are sent as before.

One possible approach:

• Split config.files into text and binary files in initialize().
• For the Service Worker, send the binary files in V_FS_INIT.binaryFiles, with a copy for each target. Either send them directly, or fix Copy binary files for each target in FileSystemPublisher.initFiles() #63 first and use initFiles().
• For the Web Worker, either:
  • send the binary files in V_WW_SETUP and write them as bytes in setupVirtualFiles(), or
  • send them with V_FS_WRITE after setup.

Acceptance criteria

• A binary file given to ready() is served by the Service Worker with the same bytes. This includes a public image, and a file served by the static middleware.
• The Web Worker reads the same bytes, for example when it inlines the file with ?inline.
• After ready(), the caller's ArrayBuffers keep their size and content.
• A test covers this in the browser.