chore: untrack runtime state (sandbox/reports); extend .gitignore

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016DvdRZkyCy9NJpHYDdPqmS

.gitignore

@@ -13,6 +13,8 @@ state/trading.db
 state/*.db
 state/output/
 state/logs/
+state/reports/
+state/sandbox/
 
 # os
 .DS_Store