Preserve whitespace in query, form, and multipart values

[ryanfowler]

Summary

• Stop trimming values after the first = for --query, --form, --multipart, and config query entries.
• Keep trimming only syntactic names where needed, so user-supplied leading/trailing spaces in values are preserved end to end.
• Add coverage for CLI and config parsing paths to verify the preserved whitespace behavior.

Testing

• Added focused unit tests for config query parsing, urlencoded form bodies, and multipart text fields.
• Added an integration test covering --query 'q= hello ', --form 'message= hello ', and --multipart 'note= hello ', plus cargo fmt and cargo clippy --locked --all-targets --all-features -- -D warnings passed.