Change-detectors, tautologies, source-reading tests, redundant duplicates,
mock-echo tests and dead/unrunnable tests. Per-test rationale in the lane
ledger (category + reason for every removal).
Widen the exception guard from OSError to Exception (re-raising
KeyboardInterrupt/EOFError first) so any prompt_toolkit runtime
failure degrades to input() — matching the established pattern in
masked_secret_prompt. ValueError and RuntimeError can arise from
exotic stream wrappers or event-loop issues with the same root cause:
prompt_toolkit cannot attach stdin on the terminal.
Add test_line_input_falls_back_to_input_on_any_prompt_toolkit_failure
covering the ValueError case.
Cover the prompt_toolkit runtime-failure path added in the fix commit: a
tty-reporting stdin where prompt_toolkit raises OSError(22) (macOS kqueue
EINVAL on fd 0 under curl|bash installs) must degrade to input() instead
of aborting the setup wizard.
