feat(dummies): add collection and tuple generators

[Reefact]

Summary

Extends the Dummies DSL from scalars to collections — ListOf, ArrayOf, SequenceOf, SetOf, DictionaryOf, plus PairOf/TripleOf — as combinators over any element generator, keeping the library's build-to-satisfy, fail-eagerly contract.

Type of change

• Bug fix
• New feature
• Breaking change
• Refactoring
• Analyzer / diagnostic change
• Tests
• Documentation

Changes

• Generators (Any.*, combinators deriving their random context from the element generator, ambient fallback — like Combine): ListOf → List<T>, ArrayOf → T[], SequenceOf → IEnumerable<T> (fully materialized), SetOf → HashSet<T>, DictionaryOf → Dictionary<K,V>, plus PairOf/TripleOf → value tuples (in-box on netstandard2.0). Comparer overloads for SetOf/DictionaryOf, and Distinct(comparer).
• Shared count engine CountSpec, mirroring the string length algebra: WithCount/WithMinCount/WithMaxCount/WithCountBetween/NonEmpty/Empty, with eager conflict detection. An unconstrained collection holds 0..8 elements (smaller spread than a string's, since elements are themselves generated values).
• Distinctness contract (see ADR-0013): a new internal ICardinalityHint lets small-domain generators (ordinal spec + bool/enum/char/guid pools) advertise an upper-bound cardinality, so a count beyond it fails eagerly with ConflictingAnyConstraintException; unknown/large domains use a bounded dedup-draw that surfaces a genuine shortfall as AnyGenerationException naming the seed. The bound stays sound under a custom comparer.
• Containment: Containing(value) forces required elements in (budgeted like string fragments); ContainingAny(generator) forces a drawn value in — named apart because a library generator both is an IAny<T> and converts implicitly to its value, which would make a single overload ambiguous.
• Tests: new AnyCollectionTests (count family + conflicts, distinct eager/fallback, comparer, containing, dictionary, pair/triple, reproducibility, As/Combine composition); the seed reproducibility batch now spans a list and a set.
• Docs: NuGet readme gains a collections bullet; ADR-0013 drafted (EN + FR) and indexed.

Testing

• dotnet build FirstClassErrors.sln — succeeded, 0 warnings (both netstandard2.0 and net8.0 legs), re-verified after rebase onto main.
• dotnet test FirstClassErrors.sln — all green (Dummies 145; FCE 423; Analyzers 85; GenDoc 155; Binder 75; Cli 64).
• Analyzer tests pass (FirstClassErrors.Analyzers.UnitTests) — ran as part of the full suite above.

Documentation

• Public API / error documentation updated — full XML docs on the new public surface.
• README / doc/ updated — Dummies/README.nuget.md and ADR-0013.
• French translation (doc/handwritten/for-users/README.fr.md) updated if user-facing behavior changed
• No documentation change required

The handwritten EN/FR user guides are intentionally left for later, per ADR-0011's follow-up ("write the user documentation once the V1 surface stabilizes"); only the packaged NuGet readme is kept current here.

Architecture decisions

• No architectural decision in this pull request
• New decision recorded — ADR drafted as Proposed: ADR-0013
• Supersedes an existing ADR — successor proposed, status not flipped: ADR-____
• ⚠️ Conflicts with an existing ADR — flagged for the maintainer: ADR-____

Rebased onto main and renumbered the ADR 0012 → 0013 after ADR-0012 (binder options, #174) landed on main.

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