* fix(deps): export and cap every engine extra
* fix(deps): docstring main and tighten export pairing tests
Give check_exports.main the required public docstring, annotate the
dependency export test helpers, and require --extra to sit with its -o
on the same just lock line (whisper pip-compile stays special-cased).
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Co-authored-by: Jatin K Malik <jatinkrmalik@gmail.com>
