refactor(open-sse): registry consolidation + DRY media/oauth/adhoc cleanup

- Single-source registry: oauth clientId/tokenUrl, usage URLs, image/embed
  configs, search defaultModel, codex fixedPort, google token url derive.
- Remove 29 unused OmniRoute providers (registry 100→71); media intact.
- De-adhoc: codex literals → registry format/oauth flags; reasoningInject,
  image/embed openrouter headers + xai bodyFields config-driven.
- Add REGISTRY_TEMPLATE.js + expand PROVIDER_DEFAULTS/schema JSDoc.
- Baselines updated; PROVIDERS 62 + alias 90 byte-for-byte, golden snapshots.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/lib/oauth/utils/server.js

@@ -1,5 +1,6 @@
 import http from "http";
 import { URL } from "url";
+import { CODEX_CONFIG } from "../constants/oauth.js";
 
 /**
  * Start a local HTTP server to receive OAuth callback
@@ -119,7 +120,7 @@ let codexProxyServer = null;
 let codexProxyTimeout = null;
 
 const CODEX_PROXY_TIMEOUT_MS = 300000; // 5 minutes
-const CODEX_PORT = 1455;
+const CODEX_PORT = CODEX_CONFIG.fixedPort;
 
 // Pending exchange sessions keyed by state — used by server-side exchange mode
 const pendingExchanges = new Map();