Add fee/charity routing config so failure_destination slashes can split to a platform fee in accountability_vault

[1nonlypiece]

Add fee/charity routing config so failure_destination slashes can split to a platform fee in accountability_vault

Description

slash_on_miss in contracts/accountability_vault/src/lib.rs sends the entire slashed amount to failure_destination. Add an optional basis-points platform fee routed to a fee address, with the remainder going to failure_destination (e.g. charity). This supports the backend Capital Flow & Fee Reporting domain. Validate the fee bps bound and ensure the split sums exactly to staked.

Requirements and context

• Must be secure, tested, and documented
• Should be efficient and easy to review
• Add fee bps + fee address to create_vault in contracts/accountability_vault/src/lib.rs
• Split the slash between fee and failure destinations
• Validate fee bps (0..=10000) and exact summation
• Add fee-split tests in contracts/accountability_vault/src/test.rs

Suggested execution

• Fork the repo and create a branch
• git checkout -b feat/slash-fee-routing
• Implement changes
  • Modify contracts/accountability_vault/src/lib.rs
  • Add tests in contracts/accountability_vault/src/test.rs
  • Document fee model in contracts/README.md
  • Add bps bound validation
• Test and commit
  • Run tests, cover edge cases
  • Include test output and notes

Example commit message

feat: add platform fee routing to slash settlement

Guidelines

• Minimum 95 percent test coverage
• Clear documentation
• Timeframe: 96 hours

[Banx17]

@Banx17 has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

Hello team, let me tackle this issue.

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[Windowlight]

@Windowlight has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

I’m interested in this issue and believe my experience with contracts, backend systems, and frontend implementation makes me a good fit. Happy to provide updates as I work through it.

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[opepraise]

@opepraise has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

I can work on this issue. Please, assign.

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[drips-wave]

Congratulations, @Banx17! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 2, 2026.

🧑‍💻 @Banx17: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

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