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>

tests/__baseline__/verify-alias.mjs

@@ -18,11 +18,7 @@ const ALIAS_TOKENS = [
   "chutes","ark","volcengine-ark","byteplus","bpm","cursor","vx","vertex","vxp","vertex-partner",
   "gw","grok-web","pw","perplexity-web","mimo","xiaomi-mimo","xmtp","xiaomi-tokenplan","cf",
   "cloudflare-ai","fal","fal-ai","stability","stability-ai","bfl","black-forest-labs","recraft",
-  "topaz","runway","runwayml","jina","jina-ai","polly","aws-polly","agentrouter","aimlapi","aiml",
-  "novita","modal","mdl","reka","nlpcloud","nlpc","bazaarlink","bzl","completions","cpl","enally",
-  "enly","freetheai","fta","llm7","lepton","kluster","ai21","inference-net","inet","predibase",
-  "bytez","morph","longcat","lc","puter","pu","uncloseai","unc","scaleway","scw","deepinfra",
-  "sambanova","samba","nscale","baseten","publicai","nous-research","nous","glhf","bb","blackbox",
+  "topaz","runway","runwayml","jina","jina-ai","polly","aws-polly","bb","blackbox",
 ];
 
 // Sort idToAlias by key — runtime accesses by key, order is irrelevant (content-based)