Rebuild MachineOutcome as executable verification reference

[SamCT86]

Why

The prior public case study explained the system but did not let an evaluator verify meaningful fail-closed behavior directly.

What changes

• adds a bounded public mutation-outcome verifier
• adds adversarial tests for stale pre-state, incomplete readback, ambiguous transport, exact post-state reconciliation and wrong post-state
• adds a synthetic fixture only
• adds CI
• rewrites the README around a five-minute clone-and-run evaluation path

Private boundary

No production provider logic, credentials, internal IDs, incident details, schemas, recovery implementation or proprietary evaluator/runtime code are published.

Local verification

• Node 24.18.0
• node --test: 6/6 PASS
• git diff --check: PASS