Switch unused-dependency check from cargo-machete to cargo-shear

[lukevalenta]

cargo-machete only inspects each crate's own dependency tables, so it misses unused entries in the workspace root and has substring-based false negatives. cargo-shear works from the resolved dependency graph and catches both, including unused [workspace.dependencies].

Swap the tool in CI, AGENTS.md, and the ct_worker README, then clean up the dead deps shear surfaced.

Also fixes a latent TOML bug where integration_tests' homepage, repository, and description keys sat inside the cargo-machete metadata table instead of [package].

[lukevalenta]

/bonk review

[ask-bonk]

PR #255 – Switch unused‑dependency check from cargo‑machete to cargo‑shear

Summary of changes

• CI workflow (.github/workflows/rust.yml) now installs and runs cargo-shear instead of cargo-machete.
• Updated AGENTS.md and crates/ct_worker/README.md to reference cargo shear in the pre‑push checklist.
• Fixed TOML metadata for integration_tests (homepage, repository, description now correctly under [package]).
• Cleaned up dead dependencies across multiple crates (removed unused entries from various Cargo.tomls).
• Added a workspace.metadata.cargo-shear ignore for getrandom (feature‑only edge case).
• Adjusted Cargo.lock accordingly.

Verification

• Build: cargo build --workspace succeeds with no errors.
• Tests: cargo test --workspace runs all unit tests successfully (13 + 5 + 1 + 50 ≈ 69 tests, all passing).
• Unused‑dependency check: cargo shear runs without reporting any unused dependencies (no output → clean).
• No remaining references to cargo-machete in the repository.

Risks / Open items

• None identified. The switch to cargo-shear improves detection of unused workspace‑level dependencies and the repository now passes all CI checks locally.

Conclusion: The PR cleanly replaces the old tool, updates documentation, removes dead code, and passes all build, test, and lint steps. No further changes are required.

github run