Close #576

Pull Request – Add-incident-response

Title:
Add guard‑check implementation & incident‑response runbook

Description:

This PR introduces two major improvements to the YieldVault project:

1. Same‑ledger exploit mitigation

   • Added per‑user ledger‑sequence tracking (LastActionSeq) and a new VaultError::RapidAction.
   • Guard checks now reject a deposit followed by a withdraw (or vice‑versa) within the same ledger, preventing flash‑loan‑style attacks.
   • Updated deposit and withdraw functions to enforce the cooldown and emit the new error.
   • Added comprehensive tests (guard_checks_test.rs) that verify:
     • Failure when deposit and withdraw occur in the same ledger.
     • Success when the ledger is advanced between actions.

2. Operational runbook

   • Created docs/incident_response_runbook.md documenting detection, alerting, triage, mitigation, and recovery procedures for RPC degradation and transaction delivery failures.
   • Includes metric thresholds, step‑by‑step mitigation actions, recovery verification, and post‑mortem guidance.

Files added / modified

Branch: Add-incident-response
PR URL: https://github.com/teeschima/YieldVault-RWA/pull/new/Add-incident-response

Please review the changes, add any reviewers, and merge when approved. Let me know if you need any additional documentation or adjustments.