cli: avoid shell=True for npx/browser helpers #542

Job	Run time
checks / readme-snippets	12s
checks / pre-commit	31s
checks / test (3.10, lowest-direct, ubuntu-latest)	54s
checks / test (3.10, lowest-direct, windows-latest)	2m 30s
checks / test (3.11, locked, windows-latest)	5m 5s
checks / test (3.10, locked, windows-latest)	2m 19s
checks / test (3.11, lowest-direct, ubuntu-latest)	54s
checks / test (3.12, lowest-direct, ubuntu-latest)	59s
checks / test (3.11, lowest-direct, windows-latest)	3m 1s
checks / test (3.13, lowest-direct, windows-latest)	2m 28s
checks / test (3.12, lowest-direct, windows-latest)	3m 36s
checks / test (3.12, locked, ubuntu-latest)	52s
checks / test (3.11, locked, ubuntu-latest)	50s
checks / test (3.13, lowest-direct, ubuntu-latest)	58s
checks / test (3.13, locked, windows-latest)	2m 57s
checks / test (3.13, locked, ubuntu-latest)	47s
checks / test (3.10, locked, ubuntu-latest)	53s
checks / test (3.12, locked, windows-latest)	3m 24s
checks / test (3.14, lowest-direct, windows-latest)	2m 27s
checks / test (3.14, locked, ubuntu-latest)	2m 23s
checks / test (3.14, locked, windows-latest)	3m 6s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 19s
all-green	2s
	42m 27s

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