Filesystem state sync engine (docs/fs-watch.md).
The server side of FEATURE_FS, split in two:
- A shared root per watched
(path, recursive, cross_filesystem), refcounted across every sync of that root on every connection: one native watcher, one hint-driven reconciler owning the canonical metadata index, publishing immutableArc<Index>snapshots. - A per-sync engine holding only client state: the shadow snapshot
(what the client holds), the held-content map for delta bases, the
ack window, and staged
RESET … SYNCupdate assembly.
Content flows through the process-wide content-addressed blob store: once any sync reads and hashes a file, the reconciler adopts the hash and every other sync serves those bytes from memory. Native backends deliver hints (a path may have changed / rescan everything); all protocol-visible behavior lives here, so the three platforms behave identically by construction.