feat(fusion_accounting_ai): 5 new financial reports AI tools

Adds financial_reports.py tools module with 5 fusion-engine-routed
tools registered in TOOL_DISPATCH:

- fusion_run_report
- fusion_get_anomalies
- fusion_generate_commentary
- fusion_drill_down_report_line
- fusion_compare_periods

Each tool guards on 'fusion.report.engine' being in the registry and
otherwise returns a structured error so the chat agent can surface a
clear "module not installed" message.

6 new TransactionCase tests (including a TOOL_DISPATCH registration
sanity check).

Made-with: Cursor

fusion_accounting_reports/tests/__init__.py

@@ -12,3 +12,4 @@ from . import test_fusion_report_commentary
 from . import test_fusion_report_anomaly
 from . import test_reports_controller
 from . import test_reports_adapter
+from . import test_fusion_report_tools