chore(repo): add clippy to enforce warnings before they're pushed (#181)

## Summary

Adds a `clippy` pre-commit hook for Rust changes so commits fail if
clippy emits any warnings.

## Related Issues

N/A

## Changes

- Added a local `clippy` hook to `.pre-commit-config.yaml` that runs
`rustup run nightly cargo clippy --workspace --all-targets -- -D
warnings`.

## Type of Change

- [ ] Bug fix (non-breaking change that fixes an issue)
- [ ] Feature (non-breaking change that adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation (updates to docs, specs, tutorials, or comments)
- [ ] Refactor (code change that neither fixes a bug nor adds a feature)
- [ ] Performance (change that improves performance)
- [ ] Test (adding or updating tests)
- [x] Build/CI (changes to build process or CI configuration)

## Affected Crates

- [ ] `lambda-rs`
- [ ] `lambda-rs-platform`
- [ ] `lambda-rs-args`
- [ ] `lambda-rs-logging`
- [x] Other: repo dev tooling (pre-commit)

## Checklist

- [ ] Code follows the repository style guidelines (`cargo +nightly fmt
--all`)
- [ ] Code passes clippy (`cargo clippy --workspace --all-targets -- -D
warnings`)
- [ ] Tests pass (`cargo test --workspace`)
- [ ] New code includes appropriate documentation
- [ ] Public API changes are documented
- [ ] Breaking changes are noted in this PR description

## Testing

**Commands run:**

```bash
pre-commit validate-config .pre-commit-config.yaml
```

**Manual verification steps (if applicable):**

1. N/A

## Screenshots/Recordings

N/A

## Platform Testing

- [x] macOS
- [ ] Windows
- [ ] Linux

## Additional Notes

- The hook uses `rustup run nightly ...`, matching the existing `fmt`
hook, so contributors will need the `nightly` toolchain available for
pre-commit to run clippy.

Author: vmarcella

.pre-commit-config.yaml

@@ -21,3 +21,9 @@ repos:
         language: system
         name: Linting for lambda-rs & tools.
         types: [rust]
+      - id: clippy
+        entry: rustup run nightly cargo clippy --workspace --all-targets -- -D warnings
+        language: system
+        name: Clippy for lambda-rs & tools.
+        pass_filenames: false
+        types: [rust]