chore: clean up stray .md files — delete junk, move chaos doc

- Delete apps/explorer-web/test-results/ (stale Playwright snapshots)
- Delete scripts/dev/dev-utils-README.md (orphaned from deleted dev-utils/)
- Move infra/scripts/README_chaos.md → docs/9_security/3_chaos-testing.md

scripts/dev/dev-utils-README.md

@@ -1,11 +0,0 @@
-# Development Utilities
-
-This directory contains utility files and scripts for development.
-
-## Files
-
-- **aitbc-pythonpath.pth** - Python path configuration for AITBC packages
-
-## Usage
-
-The `.pth` file is automatically used by Python to add paths to `sys.path` when the virtual environment is activated.