_maybe_follow_capture() issued a follow-up screenshot unconditionally
when capture_after=True, even when res.ok=False. The model then received
a normal-looking screenshot alongside an error message, and in practice
it often ignored ok=False and proceeded as if the action had succeeded.
Fix: return _text_response(res) early when res.ok is False so the model
receives only the error and can decide how to recover.
Tests added:
- test_capture_after_skipped_when_action_failed: patches click to return
ok=False and asserts no capture call is issued.
- test_capture_after_fires_when_action_succeeds: ensures the happy path
still triggers the follow-up capture.
fbdca64f73