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>

open-sse/services/provider.js

@@ -1,13 +1,14 @@
 import { PROVIDERS } from "../config/providers.js";
+import { OPENAI_COMPAT_BASE, ANTHROPIC_COMPAT_BASE } from "../providers/shared.js";
 
 const OPENAI_COMPATIBLE_PREFIX = "openai-compatible-";
 const OPENAI_COMPATIBLE_DEFAULTS = {
-  baseUrl: "https://api.openai.com/v1",
+  baseUrl: OPENAI_COMPAT_BASE,
 };
 
 const ANTHROPIC_COMPATIBLE_PREFIX = "anthropic-compatible-";
 const ANTHROPIC_COMPATIBLE_DEFAULTS = {
-  baseUrl: "https://api.anthropic.com/v1",
+  baseUrl: ANTHROPIC_COMPAT_BASE,
 };
 
 function isOpenAICompatible(provider) {