v0.2.1

What's Changed

• Added params= support for mappings with sequence values, repeated
  key/value pairs, raw query strings, and preserving existing URL query
  parameters plus fragments.
• Added response status flags: is_success, is_redirect,
  is_client_error, is_server_error, and is_error.
• Added keep-alive reuse integration tests for sync and async clients to
  protect connection reuse behavior.
• Added TLS integration tests for HTTPS happy path and certificate validation
  failure behavior without relying on external network services.
• Documented client lifecycle rules: lazy transport creation, context manager
  ownership, repeated close safety, closed client behavior, graceful sync
  close(), async cancellation, and sharing guidance.
• Documented the current timeout model: client-level connect, request-level
  pool and total, and reserved read/write fields for future streaming
  work.
• Added focused request builder tests for sync/async parity, query params,
  headers, body handling, no-mutation behavior, and no transport creation
  during build_request().
  Full Changelog: v0.2.0...v0.2.1