The base is FilmCraft's filmcraft-cfb (reader, writer, tests) at
filmcraft 6d5269ed. Ported on top of it, each with a test:
From GridCraft's and DeckCraft's readers: only sector shifts 9 and 12;
a file that ends inside its last sector still reads; a chain loop
shorter than the stream is an error instead of repeated data; a damaged
mini stream no longer fails the open; links to missing directory
entries are ignored; a stream size cap (Limits, default 1 GiB, and a
per-call cap); a lenient directory scan (directory_names,
has_entry_named) for files too damaged to open.
From WordCraft's guard: a FAT sector listed twice is refused; spare FAT
sectors and zero-padded DIFAT sectors are accepted.
New: Limits::max_dir_entries, walk() and path() to list entries,
has_stream, Writer::stream_at and write_streams, and only storages the
root reaches are walked.
