Bugfix: The fl_path_canonical() is not consistently resetting canonical.used.

Bugfix: The fl_path_canonical() is not consistently resetting canonical.used.

The `fl_path_canonical()` is replacing the `canonical` variable rather than appending to it.
However, when `path.used` is 0, then the current path is appended without resetting `canonical.used` to 0.

Ensure that `canonical.used` is always set to 0 to enforce replacement.

Add explicit documentation comment making it clear that this function performs a replacement rather than an append.