test(gc): retire the obsolete #7254 pin in gc_instrument_smoke.sh — #4644 reclassified the reproducer (output byte-identical to node under the pairing); positive live arm instead

[proggeramlug]

Tooling/test only: scripts/gc_instrument_smoke.sh arm 5b and one changelog line. Fixes the gc-stress fan-in red on main (issue #9974, item 4).

Why

Arm 5b pinned #7254's reproducer (test-files/test_gap_repsel_p4a3_ptr_numarray.ts) as "must still panic with stale forwarded pointer under PERRY_GC_SCHEDULE_RATE=1 + PERRY_GC_VERIFY_EVACUATION". It stopped panicking, and the fan-in has been red since 616a2cb. A git bisect run with the smoke script itself as the predicate (release build + the script per step, no skips) names the first silent commit: 9f790a5 (#4644, "allow retained array-growth aliases in copying verification") — the copying-minor verifier now admits a forwarded pointer whose both ends are retained growth arrays, which is exactly the Ptr growth alias #7254's reproducer exercises. #4644's changelog calls the old abort a false positive; this PR proves it for the reproducer: under the pairing the program's stdout is byte-identical to node's and the run is live (12,528 objects copied under the verifier).

What changes

The pinned-regression block is replaced by a positive arm with the same non-vacuity discipline: the #7254 file under the pairing must exit 0, print node's output, and copy > 0 objects under the verifier (the new line: correct output vs node, exit 0, 12528 objects copied under the verifier (live retained-growth coverage)). Two sentences of history stay in the script (#7254 → #4644 → this arm). The file remains in the ordinary repsel matrix corpus (test-parity/gc_repsel_corpus.txt). Arms 1–4, 5a and 6 are untouched.

Verified locally (macOS arm64)

Full scripts/gc_instrument_smoke.sh run: rc 0 with the new arm reporting; bash -n, diff-check, file-size clean. On Linux the fan-in's smoke step is the proof (local ladder).

Smoke recipe note for future readers: the script exports PERRY_GC_SCHEDULE_ALLOC_KB=0 and PERRY_NO_AUTO_OPTIMIZE=1 globally; a hand-copied arm-5 recipe without them is silent on every tree.

https://claude.ai/code/session_011dhBmdn4vGgNibjo3oZqTo

[coderabbitai]

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• changelog.d/4644-retained-growth-verifier.md
• scripts/gc_instrument_smoke.sh

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[proggeramlug]

Landed on main via merge train #9978. Validated as a tree: 77 of 80 lint gates pass, and perry-runtime/codegen/hir/stdlib all green (5,980 tests, 0 failures).

The three non-passing gates are accounted for: public-baseline is pre-existing on main (verified on a pristine worktree; red since 2026-07-29), and the two API docs gates are an artifact of this session's CARGO_TARGET_DIR override — regen_api_docs.sh hardcodes $ROOT/target/release/perry. With the binary placed where the script expects, regeneration succeeds and the drift check is clean. Thanks!