Fix all clippy warnings across workspace

collapsible_if, let-chains, derivable_impls, clone_on_copy, useless_vec, approx_constant, io_other_error, single_match, collapsible_match, unnecessary_map_or, manual_is_multiple_of, result_large_err, too_many_arguments, upper_case_acronyms

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

crates/xserial-core/src/frame/length.rs

@@ -324,7 +324,7 @@ mod tests {
         let mut f = LengthPrefixedFramer::new(cfg);
         // Corrupt frame: claims 200 bytes, actual payload is 0xFF bytes
         let mut data = be2(200);
-        data.extend_from_slice(&vec![0xFFu8; 200]);
+        data.extend_from_slice(&[0xFFu8; 200]);
         // Followed by valid frame
         data.extend(&be2(3));
         data.extend_from_slice(b"foo");