Align websocket beta header and stream completion handling with upstream behavior.
Emit completion on response.done/response.completed, surface wrapped websocket
errors without status, fail fast on response.failed, and abort websocket reader
tasks after parser exit to avoid lingering sockets. Update wire compatibility
fallback floor to 0.101.0 with regression coverage.
Clamp wire-facing client version to 0.98.0 for User-Agent and /models client_version when local builds report older versions like 0.0.0.
Adds regression tests for UA and remote model query behavior.
Fixes#539