feat(fusion_accounting_ai): wire ReportsAdapter fusion paths to engine

Adds three new method families on ReportsAdapter that route through
fusion.report.engine when fusion_accounting_reports is installed:

- run_fusion_report (pnl/balance_sheet/trial_balance/general_ledger)
- get_anomalies (variance detection on engine output)
- get_commentary (LLM narrative; falls back to templated)

These coexist with the legacy ref_id-shaped run_report / export_report
API so existing reporting tools (profit_loss, balance_sheet, etc.) keep
working unchanged. FUSION_MODEL is updated to fusion.report.engine so
mode detection picks FUSION when the new engine is installed.

4 new TransactionCase tests cover the fusion + community paths.

Made-with: Cursor

fusion_accounting_reports/tests/__init__.py

@@ -11,3 +11,4 @@ from . import test_commentary_generator
 from . import test_fusion_report_commentary
 from . import test_fusion_report_anomaly
 from . import test_reports_controller
+from . import test_reports_adapter