readDir was slicing the serialized dir entry bytes at the raw byte
boundary, splitting entries mid-stream. The plan9 client's dirUnpack
stops on a truncated entry, so 9pfuse received nothing usable.
Fix readDir to return only complete entries per read, as required by
the 9P spec. Also warn-and-skip on ExtractMetadata errors in LoadAll
instead of aborting the entire directory walk.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>