[codex] add richer sample scenario pack

[stacknil]

Summary

• add a richer scenario-pack config and bundled input alongside the existing default sample
• commit reproducible CSV and PNG outputs for the new scenario path
• document the new README entry point and cover it with an e2e reproducibility test

Scenario pack

The new sample path combines four compact phases:

• normal background activity
• a login-failure burst
• a high-risk configuration change followed by policy denials
• a rare malware-alert repeat sequence

Validation

• pytest

Notes

• default sample outputs are unchanged
• the richer sample path currently produces 28 normalized events, 24 windows, and 8 alerts
• the richer sample config uses a 120 second cooldown to keep the scenario output compact and explainable

Fixes #11