[TS PBT] Pin capability-first real property candidate

[CaelmBleidd]

Problem

The first #356 development manifest includes real properties whose Set, flat, and every operations may leave no common supported symbolic denominator for #405. Source selection must be based on language/API capability before measuring fault-finding results.

This child checkpoint

• Screen pinned real fast-check suites by original generator relationships, source operations, and license. Record why IgniteUI wrap remains concrete-only with its currently unsupported orderedPair, and why other candidates are outside the bounded core.
• Pin the unchanged helpers4 isNonEmpty implementation and original Vitest/fast-check suite at 9deb33a6f6cdab3c03404217aa8e87626930733e, with verified Git blob IDs and complete LGPL/GPL notices.
• Add a separate bounded dense integer-array subset (length 1..8, entries -16..16) that keeps the original expect(isNonEmpty(arr)).toBe(true) assertion. Record the original fc.anything support and altered distribution separately.
• Keep the second upstream indexed-access assertion outside the proposed core subset until arr[0]/toBeDefined conformance is checked. Preserve all development v1 fixtures and selection history.

Verification

At 0f9a84cd3d3298d943f514f4ccf30eb0b616ab57:

• npm install --package-lock-only --ignore-scripts --no-audit --no-fund and npm ci --ignore-scripts --no-audit --no-fund: passed in the isolated candidate directory.
• npm run validate: passed, unchanged upstream suite 3/3 tests and bounded subset 1/1 test.
• git hash-object for the unchanged implementation and suite matched pinned upstream Git blob IDs.
• Candidate JSON parsed and git diff --cached --check passed.

Capability boundary

This is a development v2 candidate, not admitted to the six-mode paired denominator yet. Direct EtsIR mapping, original-predicate symbolic search, and replay have not been run on this exact SUT; array-domain projection alone does not prove those capabilities. #395 owns registration of the original callback. The candidate has no known fault/mutant and demonstrates no feedback advantage. No production API or shared contract changes are included. #356/#357/#404/#405 remain open.

Stacked on draft #406 (caelmbleidd/pbt-356-core-corpus), pending its integration. Refs #345 #356 #395 #405.