feat: refocus on drawings — code/ADA gated off, drawing-integrity wave, Brain-directed clarification

- ENABLE_CODE_REVIEW flag (default off): skips code/ADA/jurisdiction review
  path in both pipelines; nothing deleted, one env flag to restore.
- Per-sheet Drawing Integrity QA wave (agent + classic, default on):
  dangling refs, on-sheet contradictions, dimension sanity, missing sheet
  essentials, tag hygiene. New DrawingIntegrityAgent + classic stage.
- Broadened conflict critic: intra-sheet + same-discipline contradictions,
  not just cross-discipline.
- Wave 6.5 Brain-directed clarification (bounded hub-and-spoke): Brain names
  uncertain findings, verify_evidence requests route through the wave-5b
  verifier; refuted findings suppressed. One planning call + capped verifies,
  single iteration. Shared _build_verify_scopes across 5b and 6.5.
- Config knobs, .env.example, frontend copy, tests (182 passing).

tests/test_drawing_integrity_classic.py

@@ -0,0 +1,52 @@
+"""Tests for the classic-path drawing_integrity_review stage + gating."""
+
+import backend.pipeline.drawing_integrity as di
+from backend import config
+from backend.pipeline.drawing_integrity import drawing_integrity_review
+
+
+def _sheet(page, sheet_number, n):
+    return {
+        "sheet_number": sheet_number,
+        "page_number": page,
+        "discipline": "Architectural",
+        "assertions": [{"source_text": f"n{i}"} for i in range(n)],
+    }
+
+
+def _pages(pages):
+    return [{"page_number": p, "base64": f"IMG{p}", "text_layer": f"txt{p}"}
+            for p in pages]
+
+
+def test_disabled_returns_empty(monkeypatch):
+    monkeypatch.setattr(config, "ENABLE_DRAWING_INTEGRITY", False)
+    called = []
+    monkeypatch.setattr(di, "call_stage", lambda *a, **k: called.append(1) or {})
+    out = drawing_integrity_review([_sheet(1, "A101", 5)], _pages([1]))
+    assert out == []
+    assert called == []  # no LLM calls when disabled
+
+
+def test_reviews_only_dense_sheets(monkeypatch):
+    monkeypatch.setattr(config, "ENABLE_DRAWING_INTEGRITY", True)
+    monkeypatch.setattr(config, "INTEGRITY_MIN_ASSERTIONS", 3)
+    seen_sheets = []
+
+    def fake_call_stage(system, user, subs=None, images_b64=None, **k):
+        # Record which sheet_meta reached the model.
+        seen_sheets.append(subs["sheet_meta"])
+        return {"issues": [
+            {"severity": "medium", "confidence": "high",
+             "category": "on_sheet_contradiction", "sheets": [],
+             "description": "plan disagrees with same-sheet schedule"},
+        ]}
+
+    monkeypatch.setattr(di, "call_stage", fake_call_stage)
+    sheets = [_sheet(1, "A101", 5), _sheet(2, "A102", 1), _sheet(3, "A103", 4)]
+    out = drawing_integrity_review(sheets, _pages([1, 2, 3]))
+    # Two dense sheets reviewed, one skipped; each produced one anchored finding.
+    assert len(out) == 2
+    assert all(f["source_stage"] == "drawing_integrity" for f in out)
+    assert {tuple(f["sheets"]) for f in out} == {("A101",), ("A103",)}
+    assert len(seen_sheets) == 2