style: fix clippy warnings and add clippy check to CI (#321)

* style: fix clippy warnings and add clippy check to CI

Runs `cargo clippy --all-targets -- -D warnings` in the rust_crate CI
action to catch lint issues before they land.

Fixes: redundant field names, needless returns, unnecessary closures,
io_other_error, needless borrows, single_match, unnecessary_unwrap,
and adds missing safety docs.

* chore: add 'clippy' to cspell dictionary

.github/actions/rust_crate/action.yaml

@@ -13,6 +13,11 @@ inputs:
 runs:
   using: "composite"
   steps:
+    - name: Clippy
+      working-directory: ${{ inputs.working_directory }}
+      shell: ${{ inputs.shell }}
+      run: cargo clippy --all-targets -- -D warnings
+
     - name: Build
       working-directory: ${{ inputs.working_directory }}
       shell: ${{ inputs.shell }}