StripUnresolvedLinks runs before every brain_write and brain_update. Any
walk error below a linked tree's root (e.g. one unreadable subdirectory)
made it return an error, and the write was refused: the learning was
lost. Already true on main.
It now logs a warning and returns the content unchanged: a partial index
cannot tell an invented link from one into the unreadable part, so it
unwraps nothing (never inventing a resolution) and the note is written
with its links as given.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>