feat: Integrate 1.874 Master Controls into document checking

Rewritten rag_document_checker.py to use doc_check_controls table
instead of generic canonical_controls. Each MC has:
- check_question: binary YES/NO for LLM
- pass_criteria: JSONB list of concrete requirements
- fail_criteria: JSONB list of common mistakes

Flow: Regex checks (fast) → LLM verify FAILs → MC deep check (15 per doc)
MC results appear as additional L2 checks in the report.

Coverage: 571 DSE, 381 Cookie, 309 Loeschkonzept, 153 Widerruf,
147 DSFA, 125 AVV, 113 AGB, 75 Impressum = 1.874 total.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend-compliance/compliance/api/agent_doc_check_routes.py

@@ -283,10 +283,23 @@ async def _check_single_document(entry: DocCheckEntry) -> list[DocCheckResult]:
             # Main document check (full text against primary type)
             main_result = await _run_checklist(doc_text, entry.doc_type, entry.label, entry.url, word_count)
 
-            # Control Library deep check — DISABLED until doc-check-specific
-            # Master Controls with binary pass/fail criteria are available.
-            # See: zeroclaw/INSTRUCTION-master-controls-for-doc-check.md
-            # Code: compliance/services/rag_document_checker.py (ready to re-enable)
+            # Master Control deep check — 1.874 doc_check_controls with
+            # binary pass/fail criteria verified by LLM (Qwen)
+            try:
+                from compliance.services.rag_document_checker import check_document_with_controls
+                mc_results = await check_document_with_controls(
+                    doc_text, entry.doc_type, entry.label, max_controls=15,
+                )
+                if mc_results:
+                    # Add MC results as additional checks to the main result
+                    for mc in mc_results:
+                        main_result.checks.append(CheckItem(**mc))
+                    # Recompute correctness with MC results
+                    l2 = [c for c in main_result.checks if c.level == 2 and not c.skipped]
+                    l2_passed = sum(1 for c in l2 if c.passed)
+                    main_result.correctness_pct = round(l2_passed / len(l2) * 100) if l2 else 0
+            except Exception as e:
+                logger.warning("MC check skipped: %s", e)
 
             all_results.append(main_result)