nx_nishifs_cow.nx

nx_nishifs_cow.nx -- ladder C6 (the FS): CoW SNAPSHOTS for NishiFS (Merkle structural sharing, git-style). The payoff of content-addressing: a SNAPSHOT is just a root CID, and COPY-ON-WRITE means modifying a file writes a NEW object (new content -> new CID) + a NEW directory -> a NEW root CID, while the OLD root still references the OLD (unchanged) objects. So: snapshots are FREE (remember a root CID), unchanged files are SHARED across snapshots (same CID = stored once = dedup), old snapshots are IMMUTABLE (history preserved), and snapshots are ISOLATED (tampering a new object never affects an old snapshot). This is git's model. KAT 6/6: T1 CoW makes a new root (old root unchanged); T2 structural sharing/dedup (unchanged file's object is NOT duplicated -- arena does not grow, same CID); T3 snapshot immutability (root1 still reads the OLD a, root2 reads the NEW a); T4 CoW touched only the change (a's CID changed, b's CID unchanged); T5 both snapshots read the SHARED b object; T6 liar-kill + isolation (tamper a's NEW object -> root2 read fails integrity, but root1 read of a is UNAFFECTED). composes nx_sha256 (CID) + nx_syscalls. Uses an IN-MEMORY content-addressed arena (same model as the C2 file store / C4 on-disk object region; arena chosen for a self-contained sovereign KAT -- no external dirs). NEVER-BRICK (Rule 26): writes NOTHING (pure in-memory) -- cannot touch any device, by construction. expect_exit: 0 license_tier: ORIGINAL