docs: add reusable TypeScript law-array patterns

[luantaraschi]

Why

Teams will usually share law collections across generated tests, trace verification, and live monitors. The docs should show a typed reusable definition without hiding the serializable AST.

Scope

• Add an example using defineLaws.
• Show reuse in at least two execution modes.
• Keep the example dependency-free and small.
• Avoid framework-specific helpers.

Done when

The snippet type-checks under the supported TypeScript baseline.