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/agents/test_text_layer_flow.py

@@ -63,7 +63,8 @@ def _patch_pipeline(monkeypatch, finding, verify_sink):
         runner_mod, "BrainAgent",
         lambda usage: type("B", (), {
             "run": lambda self, findings, sheet_index, jurisdiction:
-                (list(findings), [])})())
+                (list(findings), []),
+            "plan_clarifications": lambda self, prioritized: []})())
 
     class _RecordingVerifier:
         name = "verify"