Rename CLI command from `aai` to `assembly` #272

Job	Run time
brew style (Homebrew formula)	45s
build + twine check	16s
brew install (real, macOS)	10m 47s
lint + typecheck + tests (py3.13)	3m 17s
pip-audit (dependency CVEs)	25s
lint + typecheck + tests (py3.12)	3m 57s
package install — real (ubuntu-latest)	1m 15s
package install — real (macos-latest)	1m 0s
pre-commit	1m 26s
lint + typecheck + tests	3s
	23m 11s

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