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/providers/registry/mistral.js

@@ -1,8 +1,25 @@
 export default {
   "id": "mistral",
   "alias": "mistral",
+  display: {
+      "name": "Mistral",
+      "icon": "air",
+      "color": "#FF7000",
+      "textIcon": "MI",
+      "website": "https://mistral.ai",
+      "notice": {
+          "apiKeyUrl": "https://console.mistral.ai/api-keys"
+      }
+  },
+  category: "apikey",
   "transport": {
-    "baseUrl": "https://api.mistral.ai/v1/chat/completions"
+    "baseUrl": "https://api.mistral.ai/v1/chat/completions",
+    "validateUrl": "https://api.mistral.ai/v1/models",
+    "quirks": { "dropClientMetadata": true }
+  },
+  media: {
+    serviceKinds: ["llm", "imageToText", "embedding"],
+    embeddingConfig: { baseUrl: "https://api.mistral.ai/v1/embeddings", authType: "apikey", authHeader: "bearer", models: [{ id: "mistral-embed", name: "Mistral Embed", dimensions: 1024 }] }
   },
   "models": [
     {