filesystem.md: paths, the node kinds dir/file/mount, the access levels
none/ro/stage/commit with grants and floors, the exact error texts, and the
rule that a granted path under one that is not is reached only by its full
path. Listings, search, indexing by tokens (480 a piece, 64 repeated),
instruction files stacked from the boundary to the start directory, skills,
and memory kept by the server for both sides. Conformance areas fs_access,
instructions and chunk_tokens, answered from a reference model of the rules.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
