Fix PTS continuity in sequences of copied streams. #9704

Job	Run time
pre-commit	3m 30s
build_details	4s
build_js	1m 25s
build_no_depopts	5m 59s
build_win32 (x64)	10m 52s
build_opam (4.14.x)	5m 4s
build_posix (debian_trixie, amd64)	16m 31s
build_opam (5.0.x)	5m 0s
build_posix (debian_bookworm, amd64)	15m 7s
lezer_parse	50s
build_posix (ubuntu_jammy, amd64)	14m 19s
run_tests (@citest)	13m 16s
build_posix (ubuntu_lunar, amd64)	15m 4s
tree_sitter_parse	55s
run_tests (@doctest)	8m 35s
build_posix (alpine, amd64)	11m 15s
run_tests (@mediatest)	12m 8s
update_doc	0s
fetch_s3_artifacts	29s
build_docker (amd64)	2m 45s
build_docker_alpine (amd64)	45s
build_docker_alpine_minimal (amd64)	41s
build_docker_minimal (amd64)	2m 13s
update_release	0s
build_docker_release-minimal	0s
build_docker_release	0s
	2h 26m 47s

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