[SC-53] Pin the Rust toolchain

[yusuftomilola]

Overview

Every contracts job in .github/workflows/CI.yaml uses dtolnay/rust-toolchain@stable with toolchain: stable. "Stable" moves — a new release can introduce clippy lints that fail -D warnings on a PR that changed nothing, and contributors locally may compile against a different version than CI.

Tasks

• Add contracts/rust-toolchain.toml pinning an exact version with the wasm32-unknown-unknown target and the rustfmt/clippy components.
• Update CI jobs to honour the pinned toolchain rather than floating stable.
• Document the upgrade process: bump deliberately in its own PR so lint churn is isolated from feature work.
• Verify compatibility with the pinned soroban-sdk version.
• Note the required toolchain in contract documentation.

Acceptance Criteria

• The toolchain is pinned and CI uses it.
• A new stable Rust release cannot spontaneously break CI.
• Local and CI builds use the same compiler version.

Notes for Contributors

Requires Rust + Soroban. Workspace: contracts/ (soroban-sdk 22, members: assetsup, contrib, multisig-wallet, multisig_transfer, asset-maintenance). Run cargo test --all, cargo fmt --all -- --check, and cargo clippy --all-targets --all-features -- -D warnings before opening a PR — CI enforces all three. Comment below to be assigned.

[chi797]

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I’m a smart contract and full-stack developer who turns complex ideas into secure, production-ready blockchain code.
With strong skills in Rust and Solidity, I build systems that are fast, safe, and built to last.
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[northersubair]

@northersubair has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

can i handle this?

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[Caneryy]

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Hello, can I work on this issue?

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Congratulations, @northersubair! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on July 30, 2026.

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[grantfox-oss]

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@northersubair's PR #1221 was approved and merged by @yusuftomilola.

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👏 Great work, @northersubair! Keep contributing to DistinctCodes.

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This issue has been completed by @northersubair as part of the Stellar Wave Program's 7th Wave 🥳

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