- second-failure marking is now required at every return point (steps 2/4/5 and
  the rule), via a canonical 'Returning the source' action. 0.9.0 only wrote the
  marker in the second-return section, so the first return wrote nothing and the
  gate read a marker that never existed — the loop now closes.
- guide description pulled back from the 0.9.0 catch-all to an explicit
  which-step request, and states a plain coding task must not surface it —
  honouring ADR 0005's narrow-don't-broaden lever and killing the noise +
  tdd/code-review contention.

version 0.9.0 -> 0.9.1; check + validate --strict green.