chore: roll up dependency updates

[sionsmith]

Summary

• Roll up the open Dependabot Cargo dependency bumps into one PR.
• Update pinned GitHub Actions cache/upload-artifact SHAs from the Dependabot PRs.
• Relax the release version guard so dependency-only Cargo changes do not require a product version bump.

Supersedes #4, #5, #6, #7, #8, #9, #10.

Local validation

• cargo fmt --all -- --check
• go run github.com/rhysd/actionlint/cmd/actionlint@latest .github/workflows/*.yml
• ruby YAML parse for workflows and dependabot config
• cargo clippy --all-targets -- -D warnings
• cargo test --all-targets
• cargo audit
• cargo run --bin gen-man -- /tmp/keito-man-dep-rollup
• cargo build --release && ./target/release/keito --version && ./target/release/keito --help >/dev/null