[SPARK-52428] Harden client module error handling

[rafafrdz]

Summary

• Replace unwrap() with ok_or_else() + ? on operation_id and response_id in reattach/release operations
• Replace unimplemented!() with Err(SparkError::NotYetImplemented(...)) for extension response types and non-Utf8 data types
• Replace unwrap() on header parsing in middleware with graceful skip + eprintln! warning
• Improve ChannelBuilder::default() fallback

Test plan

• cargo build passes
• cargo test unit tests pass
• cargo clippy passes
• cargo fmt -- --check passes