a92b5598

By: ValentinHirschi <valentin.hirschi@gmail.com>

use Schoonschip notation for composite tensor contractions

Restrict automatic dot construction to calls to rank-one-tagged vector heads.
Generic and composite contractions retain indexed factors for Schoonschip
collection; explicit dot() remains available.

Allow supplied vectors to fill retained metric ports in both factorized and
ordered contraction paths, including when metric elimination is disabled.
Preserve factored scalar coefficients and add regression coverage for all
metric/vector multiplication orders and explicit notation choices.

Update the Python API documentation and regenerate its stubs.

Validation: 358 tensor composition, contraction, parsing and printing tests pass.
Idenso Clippy with all targets and warnings denied passes. Targeted rustfmt passes.

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