feat: expand SAFE-UC-0015 (AML triage assistant) from seed to full draft

Rewrites the AML suspicious-activity triage assistant use case from a
seed stub into a complete draft following the SAFE-UC-0018 template
structure. Covers executive summary, industry context (BSA/AML, SR 11-7,
FATF), full system architecture with tool inventory and governance matrix,
7-stage kill-chain analysis, SAFE-MCP technique mappings, controls,
9-test validation plan, and operational monitoring guidance.

Author: Sachin Keswani <sachin.news@gmail.com>

Signed-off-by: Sachin Keswani <sachin.news@gmail.com>

Author: minimaverick