pub const FS_ENTRY_FILTERED: u8 = _; // 64u8Expand description
Set on a directory whose enumeration skipped at least one child the sync’s exclusion rules cover (docs/design/fs-watch.md “Ignoring”). Excluded paths are absent rather than marked, so without this a client cannot tell an empty directory from a filtered one — a file browser needs it to say “some items hidden” instead of showing a folder that looks wrong.
Prompt when it goes up, lazy when it comes down: the first excluded child costs one re-listing of its directory, while the last one disappearing clears the flag only at that directory’s next enumeration. Chasing the clear would mean re-listing on every excluded-file event, which is the cost the exclusion exists to avoid — so a client may briefly see “hidden items” on a directory that no longer has any.