_resolve_allowed_personal_dir confined a user-supplied path to PERSONAL_DIR with
os.path.abspath + os.path.commonpath. abspath normalises `..` but does NOT
resolve symlinks, so a symlink placed inside PERSONAL_DIR pointing outside it
passes the commonpath check and lets index_personal_documents read files outside
the root. Use os.path.realpath for both the base and the candidate so symlinks
are resolved before the confinement check.
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>