Add a deterministic security verifier example

[reacher-z]

Context

Verified fan-out is a core graph-engineering pattern: independent lenses should challenge a finding before it reaches a report.

Scope

Add a no-provider example with correctness, reproducibility, and security verifier lenses over synthetic evidence, followed by deterministic adjudication.

Acceptance criteria

• Use the public verifiedFanout constructor.
• Keep evidence and verdicts structured and portable.
• Show one accepted and one rejected candidate in tests or fixtures.
• Assert parallel verifier execution and deterministic output.
• Document that verifier agreement is confidence structure, not authorization.
• Add the example to CI and the examples index.