Fix: Resolve default-routes.json path via fileURLToPath (fixes #107)

[taylortom]

Fixes #107

Fix

• Resolve the default-routes.json template path with fileURLToPath() instead of new URL(...).pathname. On Windows, URL.prototype.pathname returns a value like /C:/path/... (leading slash before the drive letter), which is not a valid path when passed on to readJson/fs.readFile; it also percent-encodes characters such as spaces and #. fileURLToPath handles drive letters, UNC paths, and decoding correctly on all platforms.
• Extracted the resolution into a pure resolveModulePath(relativePath, baseUrl) util (barrel-exported from lib/utils.js) so it is unit-testable.

Testing

• Added tests/utils-resolveModulePath.spec.js: resolves a relative path against a module URL, decodes percent-encoded characters that URL.pathname leaves escaped (asserting divergence from .pathname), and reads a real file from disk. This exercises the same class of bug on POSIX CI (via percent-encoding), which the Windows-only drive-letter symptom otherwise hides.
• npx standard passes on the changed files.

[github-actions]

🎉 This PR is included in version 4.0.1 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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