fix(fuse): ipns error handling and friendly errors (#10807)

* fix(fusei/ux): check if paths exist, print err

* fix(fuse): ipns 'could not resolve'

error type changed when code got extracted to boxo, but it was not
caught because of FUSE tests do not cover IPNS in online mode

Closes #8095
Closes #2167
Closes #3013

* docs: clarify opt-in