Deterministic Settlement Integrity: Signed Payout Guardrails and Verifiable Intent Events

[chemicalcommando]

Summary

Minimal payment-integrity hardening for the assigned issue batch.

Included

• Added dedicated settlement intent integrity event (set_int) emitted on SLA calculation.
• Event payload now includes backend-verifiable integrity fields:
  • outage id
  • status/payment type
  • computed amount
  • config version hash
  • recorded timestamp
• Added explicit payout sign guardrails:
  • violated path must produce strictly negative penalty amount
  • met path must produce strictly positive reward amount
• Preserved existing two-step admin transfer flow and deterministic calculation behavior.

Closes #214
Closes #215
Closes #216
Closes #217

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@chemicalcommando Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

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