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/translator/request/openai-to-claude.js

@@ -3,6 +3,7 @@ import { FORMATS } from "../formats.js";
 import { CLAUDE_SYSTEM_PROMPT } from "../../config/appConstants.js";
 import { adjustMaxTokens } from "../helpers/maxTokensHelper.js";
 import { safeParseJSON } from "../helpers/jsonUtil.js";
+import { parseDataUri } from "../helpers/imageHelper.js";
 
 // Empty prefix matches real Claude Code behavior (no tool name prefix).
 // Previously "proxy_" was used but this is a detectable fingerprint difference.
@@ -235,11 +236,11 @@ function getContentBlocksFromMessage(msg, toolNameMap = new Map()) {
           });
         } else if (part.type === "image_url") {
           const url = part.image_url.url;
-          const match = url.match(/^data:([^;]+);base64,(.+)$/);
-          if (match) {
+          const parsed = parseDataUri(url);
+          if (parsed) {
             blocks.push({
               type: "image",
-              source: { type: "base64", media_type: match[1], data: match[2] }
+              source: { type: "base64", media_type: parsed.mimeType, data: parsed.base64 }
             });
           } else if (url.startsWith("http://") || url.startsWith("https://")) {
             blocks.push({