On Windows, `new URL(import.meta.url).pathname` returns `/C:/...`
(with a leading slash). Passing that to `path.resolve()` or
`path.join()` causes Node to prepend the drive letter again, producing
doubled paths like `C:\C:\Users\...\detect-antipatterns-browser.js`.
Replace both occurrences (puppeteer scan at ~L2690 and live detect at
~L3506) with `fileURLToPath(import.meta.url)` from `node:url`, which
correctly strips the leading slash on Windows while remaining a no-op
on POSIX.
Add regression tests verifying the source no longer uses the raw
`.pathname` accessor for local path construction and that
`fileURLToPath` handles both Windows and POSIX file URLs correctly.
Closes#95
