v1.2.0 - gpt-5.6-sol WebSocket transport

Adds plugin-owned WebSocket transport for WS-only Codex models (gpt-5.6-sol).

New (opt-in)

• ws_transport (boolean, default false): routes models in ws_models over the Codex WebSocket transport, decoupled from ua_override. Injects service_tier: "priority" automatically and translates WS frames back into the SSE stream opencode expects.
• ws_models (default ["gpt-5.6-sol"]): which models to force over WebSocket.
• ua_version (default 999.999.999): the codex_cli_rs/<version> sent on both HTTP and WS paths.

Existing enforce_residency and ua_override behavior is unchanged.