fix(dev): clear outcome for setup.sh on non-interactive input

[islandbitcoin]

Problem

dev/setup.sh runs under set -euo pipefail. When stdin is closed or not a TTY, read at the Ibex prompt hits EOF, returns non-zero, and the script exits 1 with no message (Tester docs sweep, 2026-09-14).

Change

• EOF on either Ibex read (client ID or secret) now fails with an actionable message: re-run interactively, create .env.local, or pass --skip-ibex. No partial .env.local gets written.
• New --skip-ibex flag: skips the prompt with the existing warning, so non-interactive runs have a documented safe path.
• Interactive behavior unchanged: Enter still skips, entering credentials still writes .env.local and the overrides, and the secret still isn't echoed.
• DEV.md Quick Start covers non-interactive runs.

Validation (commit 343f19f)

Ran in a temp copy of the repo with stubbed docker/yarn and temp HOME/CONFIG_PATH. No shared Docker or real services were touched.

Case	Before (origin/main; only the closed-stdin row was run, other rows read from the code)	After
closed stdin (</dev/null)	exit 1, no message	exit 1, prints the options
piped client ID, EOF before secret	exit 1, no message	exit 1, prints the options, no .env.local
--skip-ibex with closed stdin	n/a	exit 0, skip warning
piped Enter	exit 0	exit 0, skip warning
piped client ID and secret	exit 0	exit 0, .env.local and overrides written
existing .env.local with closed stdin	exit 0	exit 0
real TTY (expect), Enter	exit 0	exit 0, skip warning
real TTY (expect), client ID and secret	exit 0	exit 0, files written, secret not echoed

bash -n dev/setup.sh is clean. There are no TypeScript or GraphQL changes, so tsc, eslint, and sdl checks don't apply.

🤖 Generated with Claude Code