nx_self_build_test.nx

nx_self_build_test.nx -- THE NET, PROVEN BEFORE THE TRAPEZE. PROOF #0 (the headline): a DELIBERATE FAILED WRITE. Snapshot a temp file, overwrite it with content that FAILS its gate, run the rollback, and ASSERT the restored bytes are BYTE-IDENTICAL to the snapshot (reread + rehash + nx_blob_hash_eq). The safety net works on a deliberate failure -> the reversible-modify tier is safe to point at real source files. Also asserts (the 3-tier policy): - a DESTRUCTIVE op (W_DELETE, and W_OVERWRITE_SRC with NO backup) is DENIED - an ADDITIVE op (W_ADDITIVE) is ALLOWED - the PASS path: a gated-GREEN reversible modify COMMITS (new bytes stand) FAIL-LOUD known-answer: every assertion has a known expected value; any mismatch prints WHAT failed and exits NONZERO. Exit 0 = ALL PROVEN. The re-gate verdict is injected by the caller (two-phase begin/finish): here it is a deterministic known-answer (1 = fail, 0 = pass) -- in-process, and free of the gate-runner's hardcoded /tmp scratch paths (so concurrent ticks cannot collide on it). This exercises the SAME snapshot -> write -> re-gate -> rollback flow the production path uses. license_tier: ORIGINAL