Review follow-ups to the non-interactive plan-tune work:
- setup now lowercases + whitespace-strips the resolved decision before the
case match, so an explicit opt-in via flag/env ("YES", "Yes", " yes") is
honored instead of silently falling through to "prompt"/skip. Also accepts
on/off and 1/0.
- gstack-config rejects out-of-domain plan_tune_hooks values (anything but
prompt|yes|no) with a warning + fallback to prompt, matching the existing
value-whitelist pattern for explain_level / artifacts_sync_mode.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Garry Tan