nx_trace_merkle.nx

nx_trace_merkle.nx -- merkle-root summary of a provenance chain. Per [[feedback-end-to-end-bit-traceability-architecture]]: "federated via Merkle-root + branch fetch with per-call mutual consent." nx_trace_merkle computes the merkle-root of a chain range so cross-host verification can confirm "did your chain end with the same root as mine?" without transmitting every link. V1 ships: - struct NxMerkleNode with hash + left/right child indices - struct NxMerkleTree built from a contiguous span of trace entries - root computation (bottom-up hash composition) - verify_membership (does a given (call_id, output_hash) appear in the tree summarized by this root?) HASH COMPOSITION RULE: parent = combine(left_hash, right_hash) where combine is V1 simple-XOR-with-rotate. V2 swaps in BLAKE3 once the existing nx_blake2b primitive is wired here. The current combine is NOT cryptographically secure; V1's purpose is the STRUCTURE (merkle-tree composition + verify pattern), V2 makes the hash strong. Composes: nx_trace_log -- the entries we summarize nx_provenance_chain -- alternative source (in-memory ring) nx_methyl -- merkle roots can be methyl-marked for sharing nx_pollinate -- merkle roots travel as XENO_OBSERVATION payloads (one root verifies a whole trace range) Gap list (V1 honest perf verdict): - combine is XOR-with-rotate, NOT cryptographically secure (V2 swaps to BLAKE3 via nx_blake2b) - tree is balanced binary; odd-leaf-count uses duplicate-last pattern (standard merkle convention) - no streaming-build (whole tree built from finite range in V1)