fix: strip trailing null bytes from pbxproj before parsing

[yocontra]

Summary

Some runtimes (notably Bun) and filesystems (APFS) can produce files with trailing null byte padding after fs.writeFileSync. When the xcode library reads a .pbxproj file that has been written this way, the PEG parser fails with:

SyntaxError: Expected end of input but "\0" found.

The actual pbxproj content is valid — only trailing \0 bytes cause the parse failure.

Changes

• lib/pbxProject.js (parseSync): Strip trailing null bytes before passing to parser
• lib/parseJob.js (async parse): Same fix for the forked worker path

The fix is a single .replace(/\0+$/, '') on the file contents string, applied after readFileSync and before parser.parse().

Reproduction

1. Use Bun to run Expo prebuild (bun expo prebuild --platform ios --clean)
2. A config plugin calls withXcodeProject which triggers parseSync
3. The generated project.pbxproj has ~16KB of trailing null bytes
4. Parser throws SyntaxError: Expected end of input but "\0" found

Test plan

• Existing tests continue to pass (no null bytes = no-op regex replace)
• Files with trailing null bytes now parse successfully