arq-docs: finding model + synthetic sample finding

[fheikens]

Sub-issue of #6. Document the public 9-field finding shape (severity, confidence, problem, why-it-matters, cited evidence, recommended action w/ SQL) and include one fully-synthetic sample finding. Output shape only, not derivation.

Acceptance: finding-model page + 1 synthetic sample; no real data.

[fheikens]

⚠ Deferred / patent-review required. A patent is still to be filed. Do not document detection/diagnosis techniques, mechanisms, anything about spoofing, or how findings are derived. Stay at or below current elevarq.com depth. This item is held until the patent is filed or the maintainer clears it. See #6.