refactor(pchome): extract backlog reporter

tests/test_pchome_mapping_backlog_modularization.py

@@ -9,6 +9,7 @@ from services.pchome_mapping_backlog import (
     controlled_apply_verifier,
     evidence,
     policies,
+    reporter,
 )
 
 
@@ -161,7 +162,46 @@ def test_controlled_apply_receipt_replay_keeps_identity_and_no_write_default(tmp
     assert len(result["executor_receipt_artifact"]["payload_sha256"]) == 64
 
 
-def test_legacy_facade_is_smaller_after_fourth_p0_extraction():
+def test_reporter_keeps_legacy_identity_and_read_only_preview():
+    assert (
+        compatibility_facade.summarize_pchome_mapping_backlog
+        is reporter.summarize_pchome_mapping_backlog
+    )
+    assert (
+        compatibility_facade.build_pchome_mapping_operator_preview
+        is reporter.build_pchome_mapping_operator_preview
+    )
+    assert compatibility_facade.compact_mapping_item is reporter.compact_mapping_item
+    assert (
+        compatibility_facade._evidence_completeness
+        is reporter._evidence_completeness
+    )
+    assert (
+        compatibility_facade._build_external_benchmark_alignment
+        is reporter._build_external_benchmark_alignment
+    )
+    assert (
+        compatibility_facade._build_ai_automation_plan
+        is reporter._build_ai_automation_plan
+    )
+
+    payload = {
+        "success": True,
+        "generated_at": "2026-07-11T14:00:00+08:00",
+        "stats": {},
+        "opportunities": [],
+    }
+    summary = reporter.summarize_pchome_mapping_backlog(payload)
+    preview = reporter.build_pchome_mapping_operator_preview(payload)
+
+    assert summary["result"] == "PASS"
+    assert preview["result"] == "NO_DIRECT_MAPPING_TARGETS"
+    assert preview["safety"]["read_only_preview"] is True
+    assert preview["safety"]["executes_search"] is False
+    assert preview["safety"]["writes_database"] is False
+
+
+def test_legacy_facade_is_smaller_after_fifth_p0_extraction():
     facade = ROOT / "services/pchome_mapping_backlog_service.py"
 
-    assert sum(1 for _ in facade.open(encoding="utf-8")) < 43_600
+    assert sum(1 for _ in facade.open(encoding="utf-8")) < 43_200