[codex] Add sanitized demo finding card

[InfoSecHack]

Summary

• Adds a sanitized first-minute demo finding card using aliases only.
• Updates the recorded demo script to show concrete value before Pacu/PMapper positioning.
• Adds redaction preflight guidance and raw-artifact screen-sharing warnings.
• Links the card from the demo README.

Validation

• git diff --check
• account ID grep: no hits
• ARN grep: only the intentional redaction-preflight pattern in the runbook; no raw ARN introduced
• ./scripts/check.sh
• ./scripts/test_fast.sh: 2069 passed

Scope

Docs-only. No source code, tests, live AWS, Terraform, collectors, reasoners, or raw artifacts changed.