[TS PBT] Build a reproducible property benchmark and mutant corpus

[CaelmBleidd]

Part of #345. Uses #348 and the shared property contract from #384.

Goal

Freeze a meaningful property and mutant corpus before testing optional search hints or drawing comparative conclusions.

Scope

• Write selection criteria before evaluating engine outcomes. Use curated explanation fixtures and real open-source TypeScript programs.
• Include round-trip, idempotence, reference-equivalence and collection/relational properties where the selected programs provide meaningful examples. State the mandatory supported categories in the corpus manifest; justify absent categories rather than adding a framework to satisfy a checklist.
• Author each property once using the existing Kotlin domains and original TypeScript predicate/precondition exports.
• Keep supported preconditions pure and invocations isolated according to [TS PBT][P0] Align and simplify property execution semantics before integration #384.
• Record project revision, license, selected files/methods, property rationale and relevant domain limits.
• Add controlled mutants with stable IDs, a source change, expected violated property and at least one concrete validating witness. Identify equivalent/invalid mutants and exclude them under a documented rule before evaluation.
• Record capability and reasons for every selected case; preserve unsupported cases in the corpus inventory.
• Freeze revisions, dependency versions, seeds, budgets, properties and mutants. Separate development/pilot cases from final evaluation cases when tuning hints or phase allocations.
• Reuse existing loading/execution commands for validation; a simple manifest and runner are sufficient.

Definition of Done

• Correct fixtures and seeded faulty fixtures are concretely validated.
• Every mutant counted in the fault denominator is traceable and non-equivalence is supported by a witness.
• Corpus membership and exclusions do not depend on whether USVM wins.
• A validation command checks shared-property loading, expected concrete outcomes and essential artifact fields.
• All configurations consume the same property definitions.
• The manifest records supported categories, limits, revisions, licenses and default run settings.
• Selection/authoring may proceed while [TS PBT][P0] Align and simplify property execution semantics before integration #384/[TS PBT] Assemble the end-to-end PBT and USVM pipeline #354 are implemented; final validation uses their shared semantics.

Stateful command-sequence/model-based testing, arbitrary object generators and full coverage of every property category are outside the initial corpus scope.