- Add `get_codex_oauth_models` Tauri command reusing the managed OAuth
access token to hit `chatgpt.com/backend-api/codex/models`; HTTP and
multi-shape JSON parsing live in `services::codex_oauth_models` so the
command stays thin.
- Unify the Claude form's "fetch models" button across normal / Copilot /
Codex OAuth presets, drop the auto-load effect for Copilot in favor of
explicit clicks, and guard against stale responses with a requestId ref.
- Add Vitest coverage for both Copilot and Codex OAuth paths asserting no
request on mount and the correct account id on click; add Rust unit
tests for the four model-list payload shapes.
Jason