cont_engine: view ToTxToT (outer Contraction, inner Hadamard) via arena #1497

Job	Run time
macos-latest: clang++ Release PaRSEC	18m 22s
macos-latest: clang++ Release Pthreads	6m 5s
ubuntu-24.04: /usr/bin/g++-14 Release Pthreads	27m 56s
macos-latest: clang++ Debug PaRSEC	13m 36s
ubuntu-24.04: /usr/bin/g++-14 Debug PaRSEC	23m 14s
ubuntu-24.04: /usr/bin/g++-14 Release PaRSEC	26m 18s
ubuntu-24.04: /usr/bin/g++-14 Debug Pthreads	22m 49s
macos-latest: clang++ Debug Pthreads	15m 5s
	2h 33m 25s

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