A node:fs function handed as-is to an asynchronous mechanism
(process.nextTick(writeFileSync, ...), a bound listener, a .then) runs with
no runtime frame on its stack, so the stack filter let the write through on
a path the suite does exercise.
The spies now record every call. The test's own fixture edits go through
the real functions captured before any spy exists. The recursive rmSync of
the reports directory becomes a rename: rmSync recurses through the public
fs.rmdirSync, which is the spy by then.
Fixes#40
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
