feat(validator): anchor the deterministic gate to the project's real cost baseline (S4.0)

Every stage of validate_proposal reasoned only about numbers the proposal itself
supplied, so an internally-consistent hallucination cleared the whole gate (F3).
A new stage 0 reconciles each affected_item against the project's CostBaseline
before the CBC solve: an unknown cost code is rejected, and a real code carrying
a quantity/unit_cost outside the configured tolerance (5% default, relative to
the baseline value) is rejected. Validation, never repair.

The baseline argument is OPTIONAL (None = pre-S4.0 behaviour), but both run
paths set it: the road path projects project.cost_items, the bundle path loads
cost-baseline.json when the bundle ships one. Bundles written before the
amendment stay un-anchored, so the commons-owned goldens run byte-identically;
a baseline that exists but is malformed still raises on both loaders.

F8: the method-specific cap now comes from the METHOD_CAPS registry (measure
type -> fraction, injectable) instead of an energy_efficiency string comparison.

The baseline format and tolerance semantics were decided locally — the commons
amendment (D-A pt. 2) never arrived, exactly as in S3.2. D7 mirroring stays open.

Three portfolio fixtures quoted cost codes belonging to OTHER projects; the new
gate caught them. They now quote each project's own lines, and the two copied
REPLIES tables import the single source instead of drifting from it.

Load-bearing measured (tests/test_s40_cost_baseline_loadbearing.py), six
mutations all red: detach the reconciliation stage; detach the magnitude
tolerance; detach the road wiring; detach the bundle wiring; ignore the injected
cap registry; make the optional loader tolerant of malformed content. Control:
with the road wiring detached the repaired portfolio fixtures still pass, so
they are not masking the seam. 597 -> 612 tests.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JdwK7bQ4BZkWH4t8MRDKb4

tests/test_portfolio_budget_loadbearing.py

@@ -26,6 +26,7 @@ from pathlib import Path
 
 import pytest
 from agent_framework import Agent
+from test_portfolio import REPLIES
 
 from portfolio_optimiser.budget import (
     Budget,
@@ -42,25 +43,11 @@ from portfolio_optimiser.run import run_portfolio
 
 _PORTFOLIO_IDS = ["FV42-GSV-E1", "RV13-RAS-TP", "BRU-LAKS-REHAB"]
 
-# Per-project replies (the tested constants of tests/test_portfolio.py, unchanged): all three
-# validate, and their claimed savings are DISTINCT — which is how a run is keyed back to its
-# project here, since ``RunResult`` carries no project id. 200000 + 130000 = the first two.
-REPLIES = {
-    "FV42-GSV-E1": (
-        '{"measure":"Reduce scope","affected_items":['
-        '{"code":"05.2","quantity":4300,"unit_cost":215},'
-        '{"code":"03.1","quantity":1800,"unit_cost":310}],"claimed_saving_nok":200000}'
-    ),
-    "RV13-RAS-TP": (
-        '{"measure":"Material substitution","affected_items":['
-        '{"code":"88.2","quantity":180,"unit_cost":4200}],"claimed_saving_nok":130000}'
-    ),
-    "BRU-LAKS-REHAB": (
-        '{"measure":"Reduce scope","affected_items":['
-        '{"code":"05.2","quantity":4300,"unit_cost":215},'
-        '{"code":"07.4","quantity":2400,"unit_cost":690}],"claimed_saving_nok":210000}'
-    ),
-}
+# Per-project replies: IMPORTED from tests/test_portfolio.py rather than copied. The copy claimed to
+# be "the tested constants ... unchanged" and then drifted — S4.0's baseline anchoring caught it,
+# because the copies quoted cost codes belonging to OTHER projects. All three validate, and their
+# claimed savings are DISTINCT — which is how a run is keyed back to its project here, since
+# ``RunResult`` carries no project id. 200000 + 130000 = the first two.
 _FIRST_TWO_SAVING = 330000
 
 # Measured: 32 tokens per run at tokens=8. 80 total funds two runs (32 + 32 = 64) and leaves 16,