Shared secret-read helper for PAT (D11) and pooler URL paste (D16).
One implementation of the hardest-to-get-right pattern: stty -echo +
SIGINT/TERM/EXIT trap that restores terminal mode, read into a named
env var, optional redacted preview.
Validates the target var name against [A-Z_][A-Z0-9_]* to prevent
bash name-injection via `read -r "$varname"`. When stdin is not a TTY
(CI, piped tests) the stty branches skip cleanly — piped input doesn't
echo anyway. Exports the var after read so subprocesses inherit it;
callers own the `unset` at handoff time.
Sourced, not executed — no +x bit.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>