Add durable NUnit parity harness

RUSTREWRITE.md

@@ -322,6 +322,14 @@ observations, assertions, tolerances and expected error/event behavior. Shared
 C# test helpers become shared Rust test helpers; embedded fixtures and literal
 payloads are copied with license/source attribution and byte hashes.
 
+The parity harness is in place: every invocation has a stable source/case ID,
+parameter identity, body hash, category, fixture dependency list, Rust location,
+and semantic-review status. Reviewed tests are identified by `parity-case`
+markers in hand-written Rust files, so regeneration writes only unresolved
+placeholders and fails on body drift. The checked-in audit reports pending,
+translated, ignored-live, benchmark, drifted, missing, duplicate, stale, and
+unreviewed cases; the initial handover contains 1,295 unreviewed cases.
+
 The Rust tests must call the public APIs rather than internal replacements.
 Where the C# tests call internal members through friend-assembly access, record
 that fact and place equivalent Rust unit tests inside the owning crate without