Hit for real driving a first sign-in: `granthi-sync link` run through anything
that is not a terminal -- a wrapper, a pipe, `| tee setup.log` -- printed
NOTHING, while the code it was holding silently expired five minutes later.
Python buffers stdout when stdout is not a tty, and the two prints carrying
the verification URL and the user code did not flush.
They flush now. One regression test asserts both are printed with flush=True,
because this fails silently and only under redirection, which is exactly the
condition a test would otherwise never reproduce.
204 tests (was 203).