[TS] Support bounded sparse indexed writes with known own slots

[CaelmBleidd]

An indexed cache write such as iotaCache[2] = value into an empty array stopped the PGOrbit identity scenario at ARRAY_INDEX_GROWTH. Support non-dense indexed writes within maxArraySize when the engine already knows own-slot provenance: extend length to max(oldLength, index + 1), retain absent gaps and do not revive values deleted by shrinking.

Reuse existing presence and typed-value storage. Sparse growth revokes the existing dense-shape proof so a later shrink cannot silently re-enable dense-only models. Register the density already guaranteed by PBT ArrayDomain inputs through the existing presence helper. Capacity and unknown-provenance paths retain explicit limitations. The diagnostic regressions from #560 now exercise the remaining capacity boundary, and a separate DSL regression checks that the small sparse cache case succeeds.

Validation: 150 focused tests passed across TS array/models, PBT projection/search, DSL/native replay and Calls guard/registry/harness. Source-level coverage includes number/boolean/reference/unresolved/widened arrays, symbolic gap indices, shrink/regrow, array moves and fill. Removing only dense-proof invalidation makes its source regression fail. PBT candidate replay preserves the original dense input before mutation. TS/PBT/Calls Detekt main/test, FastCheck Detekt test and diff checks pass.

A one-shot preflight on the frozen original PGOrbit input [8,2,0,2,0,0,0,0] now reaches one terminal state past the cache write with no runtime limitations, unsupported calls, engine failures or timeout; native TypeScript accepts the same fixed property input. This is a fixed-input check, not a coverage benchmark.

Depends on #567 and #560. This PR targets #567; #560 is included as an exact prerequisite merge so its diagnostic fixtures remain compatible. The indexed-growth change is its final dedicated commit. Refs #388; the full issue remains open for direct length growth, array membership, unproven own slots, sparse transport and remaining exact output reconstruction.

CI regression follow-up: two legacy expectations still required all indexed growth to stop. They now verify the intended supported boundary: the existing element remains 22, and allocated sparse expansion reaches one terminal state with length 6, preserved values and undefined hole reads. Native replay checks that indices 3 and 4 remain absent own slots. Materializing the original sparse array still throws TsUnsupportedWitnessException at slot 3; the dense witness schema is not broadened or silently filled. Fractional, negative, and chained named-property writes retain their explicit unsupported assertions. The reported two failures were reproduced on 37a65d48b16f before editing; all 25 focused tests and DetektTest pass after the correction.