fix(s51): close 2 review MINORs — non-UTF-8 skip + affected_codes parity

Both live in the tolerant inbox-read path and both contradicted the module's
own "skipped, never raised" / loader-parity docstrings (S5.1 review: ALLOW,
2 MINOR, non-gating):

- UnicodeDecodeError (a *.json hand-saved in Latin-1 with Norwegian æ/ø/å is
  invalid UTF-8) now SKIPPED in hitl._load_json_dict AND
  verdicts.load_verdicts_from_dir — was: crashed pending/route with a raw
  traceback (a ValueError subclass, caught by neither OSError nor
  JSONDecodeError). Fix symmetric across both readers.
- hitl._inbox_verdict_ids now skips a non-iterable affected_codes exactly as
  load_verdicts_from_dir does (frozenset() raises TypeError) — was: marked the
  proposal judged on key-presence alone → a silent false-negative in the
  operator pending queue. hitl-only: verdicts is the correct reference.

TDD: 3 RED-then-green (both UnicodeDecodeError twins + the parity gap) + 1
ground-truth pin locking the loader side so the parity cannot rot.

Gate: pytest → 389 passed, 4 skipped (was 385); ruff check + format clean; mypy clean.

tests/test_hitl_loadbearing.py

@@ -193,6 +193,36 @@ def test_inbox_idset_skips_malformed_features(tmp_path: Path) -> None:
     assert [p.run_id for p in hitl.pending(str(outbox), str(inbox))] == ["run-1"]
 
 
+def test_inbox_idset_skips_non_iterable_affected_codes(tmp_path: Path) -> None:
+    """PARITY (wrong-type): an inbox verdict with every required key present but ``affected_codes`` a
+    NON-ITERABLE (``null``) is skipped — the real loader's ``frozenset(pf['affected_codes'])``
+    (verdicts.py) raises ``TypeError`` and ``load_verdicts_from_dir`` drops it. So ``pending`` must NOT
+    count it as judged; otherwise ``hitl`` marks the proposal judged while the learning pipeline still
+    treats it pending — a silent false-negative in the operator queue, the exact failure the parity
+    docstring says it prevents. Detach the ``affected_codes`` iterability check (accept on key-presence
+    alone) → the file clears pending → RED. Ground-truth twin:
+    ``test_verdicts.test_load_skips_non_iterable_affected_codes``."""
+    outbox = tmp_path / "outbox"
+    inbox = tmp_path / "inbox"
+    _write_proposal(outbox, "run-1", verdict_id="SHARED-VID")
+    _write_raw_verdict(
+        inbox,
+        "SHARED-VID",
+        {
+            "id": "SHARED-VID",
+            "decision": "approved",
+            "rationale": "ok",
+            "proposal_features": {
+                "affected_codes": None,  # non-iterable → real loader's frozenset() raises → skips
+                "measure_type": "scope_reduction",
+                "claimed_saving_nok": 200.0,
+            },
+        },
+    )
+
+    assert [p.run_id for p in hitl.pending(str(outbox), str(inbox))] == ["run-1"]
+
+
 # --- transitive import-graph MAF-freedom probe (Step 5) -------------------------------------------
 
 _SRC_DIR = Path(__file__).resolve().parents[1] / "src" / "portfolio_optimiser"