[mathiasrw]

Closes #794

Stacked on #786.

Change

• --pipe (-p) is gone. It gave the piped data to the code of --js as pipe, and did nothing useful without --js. --js-pipe does the same, and is the one to use.
• -p is free.
• The warning "Data is piped in, but no flag tells what to do with it" is gone. Only --pipe could give it: without files the piped data is the content, and with files the pipe is only read when a flag asks for it, and all the other flags use it.
• The help and the README say --js-pipe where they said --pipe.
• The devguide table of the output functions is up to date: panic() and not die(), the exit codes 1, 2 and 3, and checkFailed().

Tests

• test/cli/pipe.test.js tests --js-pipe, and that --pipe and -p are unknown (exit code 3).
• test/fix/719.test.js is gone with the warning, and so is the line in run.sh. The status report test for warnings uses 0 files found.
• yarn test-ci passes: the demo on Node and Bun, and 976 Bun tests.