feat(fase4): route the validator falsification into the next hypothesis (informed refinement)

Closes gap #5 (maalbilde §5/§7): generate_via_llm's outer max_attempts loop
built the prompt ONCE and re-sent it identically — a BLIND retry. The validator's
per-attempt Rejection.reason was captured in `last` but never reached the next
prompt, so the proposer re-answered the same question with no knowledge of WHY
the prior candidate failed. Step 5 routes that reason into the next attempt.

- generate.py: _build_messages() gains prior_rejection; when set it appends a
  revision block carrying ONLY the falsification reason verbatim (never the
  rejected proposal JSON). None -> the byte-identical base prompt, so attempt 1
  is unchanged. generate_via_llm() rebuilds messages inside the outer loop with
  prior_rejection=`last` (None on attempt 1); _fetch_parsed() takes messages as
  an explicit parameter. `last` is overwritten each round -> only the most-recent
  falsification ("forrige"), never an accumulated history. Bound unchanged:
  max_attempts + meter.tick_round (no new loop; §6 — "improve until good enough"
  without a ceiling stays impossible).
- Scope honesty: the only per-attempt falsifier here is the validator. The
  checker is a run-level, one-shot signal (run.py, before generation); seeding
  generation with the checker critique is separately scoped and NOT done here.
  The boundary is written into the generate_via_llm docstring + README + CLAUDE.

Load-bearing (maalbilde §7): tests/test_step5_refine_loadbearing.py is a PAIR —
the positive test keys the proposer's flip on the validator REASON PAYLOAD (the
rejected claim value, derived from validate_proposal(bad).reason so test and SUT
share one source of truth), and asserts the reason reached attempt 2's prompt
VERBATIM (the green-but-dead guard). It goes RED on detach (build messages once):
the flip token never arrives, so the outcome never flips AND the verbatim
assertion fails — proven double-red. The bounded control proves a never-fixed
proposer exhausts exactly max_attempts and returns a Rejection.

Adversarial Plan agent hardened the design pre-implementation (flip on payload
not wrapper/call-count; derive flip-key from the validator reason; drive through
generate_via_llm directly; docstring honesty). Suite 136->138 passed, 4 skipped;
mypy + ruff check clean. New test ruff-formatted; pre-existing ruff-format drift
(budget/verdicts/test_contracts) left untouched for a surgical diff.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MHR8iKxJRxDiDfNw8HZmWE

CLAUDE.md

@@ -46,6 +46,16 @@ Python ≥3.10. MAF (`agent-framework-core` 1.9.0). Pakkehåndtering: `uv`. To b
   aldri checkeren (de to falsifisererne blandes aldri). Load-bearing:
   `tests/test_checker_gate_loadbearing.py` blir rød ved BEGGE detach-punkt (revert `output_from`,
   eller fjern override). Checkeren «må faktisk gate, ELLER vi slutter å kalle det maker-checker».
+- **Informert forbedring, bundet (Steg 5, målbilde §5/§7):** `generate_via_llm`s ytre
+  `max_attempts`-løkke er ikke lenger blind — validatorens *forrige* `Rejection.reason` mates inn i
+  neste forsøks prompt (`_build_messages(prior_rejection=...)`), så proposeren korrigerer i stedet
+  for å gjenta. Kun den mest-nylige falsifiseringen (`last`, ikke akkumulert), kun grunnen (aldri
+  forrige proposal-JSON), under EKSISTERENDE tak (`meter.tick_round` + `max_attempts` — ingen ny
+  løkke; «forbedre til god nok» uten tak er forbudt). Eneste *per-forsøk*-falsifiserer her er
+  validatoren; å seede generering med checker-*kritikken* er run-nivå og separat scoped (IKKE bygget
+  her) — så koden påstår ikke mer enn den gjør. Load-bearing:
+  `tests/test_step5_refine_loadbearing.py` blir rød når reason-injeksjonen detaches (utfallet
+  flipper aldri + reason-verbatim-asserten faller); kontrollen beviser at løkka forblir bundet.
 - **Kostnadsdisiplin:** utvikle primært på lokal profil (gratis); Foundry/Azure (privat tenant finnes) kun til målrettet, minimal verifisering; billigste modeller + små syntetiske data + harde token-tak. Ingen tunge test-kjøringer.
 - **STATE.md er local-only** (gitignored). Voyage session-state er efemert; STATE.md er kanonisk kontinuitet.
 - Prosess: Voyage-plugin (`/trekbrief → /trekplan → /trekexecute → /trekreview`) per større fase.