feat(fase2): wire Step-1 ExpeL retrieval into the hypothesis prompt

Closes maalbilde §5 gap #1 (the one missing "feedback-into-prompt" dataflow)
for the OKF-bundle path. Before, ExpeL was computed AFTER generation into a
discarded SessionContext, so a prior verdict could not influence any hypothesis
(context_providers=0).

- New okf.py: framework-neutral OKF bundle navigation (index + frontmatter +
  cross-links), pure stdlib, no agent_framework/mcp (D7-portable), enforced by
  test_okf_is_maf_free.
- verdicts.py: seed_store_from_bundle + bundle_candidate_features build the
  ExpeL substrate + the pre-hypothesis query key from a bundle.
- run_project(bundle_dir=...): folds the candidate's prior verdicts into the
  generation context BEFORE generate_via_llm; the road path is unchanged.

Load-bearing (maalbilde §7): test_step1_expel_loadbearing proves a prior verdict
reaches the hypothesis prompt and goes RED when the fold is detached (shown via
TDD red->green). The marker is the minted verdict id (content hash) because
docs_dir==bundle_dir lets keyword chunk-stuffing leak the realization rate;
clean layer separation is Fase 2b.

Suite 121->133 passed; mypy + ruff check clean.

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

tests/test_step1_expel_loadbearing.py

@@ -0,0 +1,93 @@
+"""Step-1 load-bearing seam (målbilde §5 / §7): a prior expert verdict MUST reach the next
+hypothesis prompt.
+
+The diagnosis (fot-i-bakken, verified in code): ExpeL retrieval was computed AFTER generation and
+written into a discarded ``SessionContext`` — so the seed verdict could not influence any
+hypothesis (``context_providers`` = 0). Fase 2a wires it: before ``generate_via_llm``, the
+candidate's prior verdicts are folded into the generation context.
+
+These two tests are a load-bearing PAIR, not a smoke test (per the Fase-2 green-but-dead trap):
+- the positive test asserts the seed verdict's realization signal ("0.82") IS in the generation
+  prompt — it goes RED the moment the fold is detached;
+- the empty-store test asserts the signal is ABSENT without a seed — proving the signal's presence
+  is CAUSED by the seam, not incidental to the fixture.
+"""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+from portfolio_optimiser.run import run_project
+from portfolio_optimiser.validator import ValidatedProposal
+from portfolio_optimiser.verdicts import VerdictStore, seed_store_from_bundle
+
+BUNDLE_DIR = Path(__file__).resolve().parents[1] / "shared" / "examples" / "bygg-energi-mikro"
+
+# A VALID BYGG-KONTOR-NORD proposal: affected total = 300000 x 1.0; no assumptions -> degenerate
+# Monte Carlo P90 = 0.30 x 300000 = 90000 >= claimed 30000 -> validates on the first attempt.
+_ENERGY_REPLY = (
+    '{"measure":"LED-retrofit av kontorbelysning","affected_items":'
+    '[{"code":"ENERGI-TOTAL-EL","quantity":300000,"unit_cost":1.0}],"claimed_saving_nok":30000}'
+)
+_VERDICT_INPUT = {"decision": "approved", "rationale": "expert reviewed (sim)"}
+
+# The load-bearing marker is the seed verdict's MINTED id (a 16-char content hash that
+# ``ExpeLContextProvider.format_fewshot`` emits as ``- [<id>] ...``). It cannot appear in the
+# bundle's raw text, so its presence in the prompt isolates the STRUCTURAL ExpeL path. (The
+# realization rate "0.82" is NOT a usable marker here: ``docs_dir == bundle_dir``, so keyword
+# chunk-stuffing reads the verdict file and would leak "0.82" regardless of the fold. Layer
+# separation — verdicts out of the keyword docs folder — is Fase 2b.)
+_SEED_ID = seed_store_from_bundle(str(BUNDLE_DIR)).verdicts[0].id
+
+
+def _generation_prompts(sink: list[str]) -> list[str]:
+    """The generation-call prompts (``generate._build_messages`` embeds 'SavingsProposal'),
+    isolated from the debate-round prompts also captured in the sink."""
+    return [p for p in sink if "SavingsProposal" in p]
+
+
+async def test_prior_verdict_reaches_hypothesis_prompt(make_recording_client_factory) -> None:
+    """LOAD-BEARING: with the energi bundle's seed verdict in the store, the realization signal
+    reaches the hypothesis-generation prompt. Detach the fold in ``run.py`` and this goes red."""
+    store = seed_store_from_bundle(str(BUNDLE_DIR))
+    assert store.verdicts, "precondition: the bundle seeds exactly one verdict"
+    factory, recorded = make_recording_client_factory(_ENERGY_REPLY)
+
+    result = await run_project(
+        "BYGG-KONTOR-NORD",
+        "local",
+        docs_dir=str(BUNDLE_DIR),
+        bundle_dir=str(BUNDLE_DIR),
+        verdict_input=_VERDICT_INPUT,
+        store=store,
+        client_factory=factory,
+    )
+
+    assert isinstance(result.outcome, ValidatedProposal)
+    gen_prompts = _generation_prompts(recorded)
+    assert gen_prompts, "the generation call must have happened"
+    assert any(_SEED_ID in p for p in gen_prompts), (
+        "the seed verdict did not reach the hypothesis prompt — the ExpeL->prompt fold is detached"
+    )
+
+
+async def test_empty_store_leaves_no_signal_in_prompt(make_recording_client_factory) -> None:
+    """CAUSALITY CONTROL: the same run with an EMPTY store carries no realization signal into the
+    prompt — proving the signal above is caused by the seam, making the positive test load-bearing
+    (not merely green against the fixture's mere presence)."""
+    factory, recorded = make_recording_client_factory(_ENERGY_REPLY)
+
+    await run_project(
+        "BYGG-KONTOR-NORD",
+        "local",
+        docs_dir=str(BUNDLE_DIR),
+        bundle_dir=str(BUNDLE_DIR),
+        verdict_input=_VERDICT_INPUT,
+        store=VerdictStore(verdicts=[]),
+        client_factory=factory,
+    )
+
+    assert all(_SEED_ID not in p for p in recorded), (
+        "no seed verdict in the store, yet its id appeared in a prompt — "
+        "the assertion is not actually load-bearing"
+    )