chore(contracts): enforce fmt + clippy CI gate and clear all lint/format lapses

[EmeditWeb]

…mat lapses

Contracts CI previously ran only build + test — nothing guarded formatting or lints, so 91 rustfmt hunks and 27 clippy warnings had accumulated across all six contracts. This adds the missing gates and brings the tree clean so every future PR is held to the same bar.

CI (.github/workflows/contracts-ci.yml):

• Add cargo fmt --all --check (fast fail, before any compile).
• Add cargo clippy --workspace --all-targets -- -D warnings, placed after the dependency-WASM build so creditline's contractimport! clients resolve during the native clippy compile (otherwise E0599 on receive_guarantee).
• Install rustfmt + clippy toolchain components.

Formatting:

• Apply rustfmt across all six contracts.

Lint fixes (clippy -D warnings now clean):

• Replace assert_eq!(x, <bool>) with assert! in liquidity-pool and creditline tests (10).
• Use saturating_add in place of checked_add(..).unwrap_or(u64::MAX) in vouching TTL math — behaviour-identical (2).
• Use matches! in place of match-to-bool in creditline reputation-call handling (2).
• Remove unused Val/Vec imports, an unused mut, an unused registry binding; add an elided lifetime; fix a rustdoc list-item indentation.
• Remove the dead safe_math modules from parameters and vendor-registry: both already perform overflow-checked arithmetic inline, so no safety is lost. creditline, liquidity-pool and reputation keep their used copies.
• Remove an unused assert_event test helper.

Test quality:

• Add the missing share_price_before == 10_000 baseline assertion in the creditline default-loss test (the value was captured but never checked).

Verified: fmt clean, clippy -D warnings clean, all contracts build for wasm32-unknown-unknown (release), 420 tests pass.

Summary

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