Clean up tensor contraction APIs

[shinaoka]

Summary

• pin tensor4all-rs to the merged tenferro-rs integer-label einsum/read-view API
• consolidate TensorDynLen contraction paths and benchmark tensor/TT operation overheads against Julia/tenferro
• align Krylov/linsolve behavior and add coverage for contraction, TensorTrain, TreeTN, tensor backend, and GMRES edge paths

Verification

• cargo fmt --all -- --check
• cargo nextest run --release --workspace
• cargo test --doc --release --workspace
• ./scripts/test-mdbook.sh
• cargo llvm-cov --workspace --exclude tensor4all-hdf5 --json --output-path coverage.json && python3 scripts/check-coverage.py coverage.json