feat(voice): add ChatGPT OAuth auth option

docs/CURRENT-STATE.md

@@ -3607,7 +3607,7 @@ silently demoting every later lookup for the session.
 
 `GEV MIC` button (bottom UI) starts an OpenAI Realtime session over WebRTC:
 
-- **Token flow**: browser fetches a short-lived client secret from `/api/realtime/token`; the Vite middleware holds `OPENAI_API_KEY` and posts the full session config (instructions, tool schemas, VAD, truncation) to `api.openai.com/v1/realtime/client_secrets`. SDP exchange goes directly to `api.openai.com/v1/realtime/calls` with the ephemeral token.
+- **Token flow**: browser fetches a short-lived client secret from `/api/realtime/token`; the Vite middleware uses `OPENAI_API_KEY` by default, or the signed-in local ChatGPT/Codex OAuth access token when OAuth was explicitly selected in Provider Settings, and posts the full session config (instructions, tool schemas, VAD, truncation) to `api.openai.com/v1/realtime/client_secrets`. Both long-lived credentials stay server-side; OAuth minting is loopback-only. SDP exchange goes directly to `api.openai.com/v1/realtime/calls` with the ephemeral token.
 - **Session defaults** (env-tunable): model `gpt-realtime-2` (or `gpt-realtime-2.1-mini` when the MINI tier is selected — see the model-tier entry below), voice `marin`, reasoning effort `low`, semantic VAD with low eagerness, no response interruption, context window truncated to ~3,000 post-instruction tokens with 0.5 retention ratio — the conversational window stays short because map state is fetched live per turn.
 - **Twenty-nine tools** (argument schemas in `src/voice/actionSchemas.js`, served with their descriptions by `server/providers/openai/tools.js`, executed client-side in `src/voice/gevActions.js`): `fly_to_location`, `select_nearest_aircraft`, `adjust_camera_zoom`, `zoom_to_globe`, `set_layer_visibility`, `show_data_layers_menu`, `set_panel_open`, `set_visual_style`, `get_entity_context`, `get_current_view_state`, `set_hud`, `set_detection`, `set_map_stack`, `set_post_processing`, `control_scene`, `control_cctv`, `set_context_mode`, `control_cockpit`, `control_radio`, `track_entity`, `stop_tracking`, `frame_overhead`, `annotate_map`, `clear_annotations`, `move_camera`, `fly_route`, `analyst_query`, `next_iss_pass`, and `next_satellite_pass`.
 
@@ -3653,7 +3653,7 @@ silently demoting every later lookup for the session.
   2. **Contacts OFF** → "nearby" means **in view**; "near \<place\>" means a radius around that place. A radius query with Contacts active and no explicit centre is centred on the **active contact**, not the camera.
   3. **Every count names its scope in words** — "42 in your window", "8 in view", "about 30 within 250 km of Austin" — never a bare number. `analyst_query` returns `scopeLabel` so this is mechanical. Two different numbers with named scopes are not a contradiction.
   4. **The loaded-data caveat is stated once when relevant**: counts cover loaded data, and the flights layer loads where you look (appended to `coverage.note` for radius/view scopes over viewport-loaded layers).
-- **Degradation**: without `OPENAI_API_KEY`, `/api/realtime/token` returns 503 and the mic button surfaces the error; the rest of the app is unaffected.
+- **Degradation**: API-key mode without `OPENAI_API_KEY` returns 503 as before. Selecting OAuth without a usable local ChatGPT/Codex sign-in starts the local `codex login` browser flow, polls for the resulting local token, and selects OAuth when sign-in completes. If the Codex login flow cannot start or does not complete, the rest of the app is unaffected.
 
 ### AI HUD Summary (June 2026)
 
@@ -3835,7 +3835,7 @@ are omitted rather than framing the wrong part of the globe.
 - GBFS proxy refuses upstream redirects (`redirect: 'manual'`; any 3xx becomes a 502 and the redirect target is logged server-side only) and enforces its 5 MB response cap while the body streams, cancelling the upstream read past the cap; CCTV health map is bounded.
 - Proxy error payloads are sanitized (no internal error details returned to clients).
 - That holds for the OpenAI and CCTV media paths too: `/api/openai/hud-summary` never relays OpenAI's own `error.message`, `/api/realtime/token` passes successful ephemeral-token responses through but answers with a fixed error when minting fails or upstream rejects the request, and a failed CCTV media fetch stores a fixed camera health `message` — `GET /api/cctv/health` serializes that field and the CCTV panel renders it as a status label, so it is a client surface as much as the response body is.
-- `OPENAI_API_KEY` is server-side only; the browser receives ephemeral Realtime client secrets from `/api/realtime/token`.
+- `OPENAI_API_KEY` remains server-side only and remains the default voice credential. The optional OAuth mode reads the local ChatGPT/Codex access token server-side on loopback only; the browser receives only ephemeral Realtime client secrets from `/api/realtime/token`.
 - `AISSTREAM_API_KEY` is server-side only; the browser reads the same-origin `/api/ais-live` cache.
 - `/api/google/nearby-places` keeps the Google key out of Places requests issued for voice scene context.
 - `/api/google/text-search` keeps the Google key server-side for view-biased Places recovery used by annotation resolution.