Function computeSecurityReviewCounters

computeSecurityReviewCounters(
    contracts: readonly ContractModelContract[],
    expiringWithinDays: number,
    now: Date,
    undocumentedContractCount: number,
    undocumentedVariableCount: number,
): SecurityReviewCounters
Computes every number renderSecurityReview() reports, as real data.
Parameters
- contracts: readonly ContractModelContract[]
- expiringWithinDays: number
- now: Date
- undocumentedContractCount: number
- undocumentedVariableCount: number
Returns SecurityReviewCounters

Remarks
Previously this arithmetic lived entirely inside the renderer as closure locals that only ever became interpolated Markdown text -- no exported type backed any of it, so nothing downstream (the --json envelope, a CI gate, a future Finding Model adapter) could consume it as data. Extracted so it can be reused wherever these facts are needed, not just prose.
- Defined in src/build/docs.ts:718