refactor(open-sse): B1 consolidate media endpoint URLs into registry

- image/embed/tts/search base URLs derive from media.*Config.baseUrl /
  searchViaChat.endpoint (single source); handlers read PROVIDER_MEDIA.
- ~18 hardcoded endpoints moved: bfl/fal/stability/runway/hf/gemini/
  cloudflare/recraft/sdwebui/comfyui/nanobanana image, voyage embed,
  gemini/openrouter tts, chatSearch endpoints.
- Byte-identical: PROVIDERS 62 + alias 90 baselines, image buildUrl outputs.

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

open-sse/providers/registry/xai.js

@@ -25,7 +25,7 @@ export default {
   },
   media: {
     serviceKinds: ["llm", "imageToText", "webSearch", "image"],
-    searchViaChat: { defaultModel: "grok-4.20-reasoning", pricingUrl: "https://x.ai/api#pricing" },
+    searchViaChat: { defaultModel: "grok-4.20-reasoning", endpoint: "https://api.x.ai/v1/responses", pricingUrl: "https://x.ai/api#pricing" },
     imageConfig: { baseUrl: "https://api.x.ai/v1/images/generations", bodyFields: ["model", "prompt", "n", "response_format"] },
     authModes: ["oauth", "apikey"],
     hasOAuth: true