Added TDD bug-capture tests proving that `agents init --yes` fails to
bypass the migration approval prompt in a TTY environment (bug #783).
Behave scenarios in features/tdd_init_yes_no_input.feature and Robot
Framework tests in robot/tdd_init_yes_no_input.robot exercise the real
`init --yes` code path with sys.stdin.isatty() mocked to True and no
stdin input available. With the bug present, the migration runner
calls typer.confirm() despite --yes, and the empty stdin causes the
migration to be declined (MigrationNotApprovedError).
All tests are tagged @tdd_expected_fail @tdd_bug @tdd_bug_783 so CI
passes while the bug remains unfixed. The bug fix developer will
remove @tdd_expected_fail when the fix is implemented.
ISSUES CLOSED: #842
hurui200320