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/executors/opencode-go.js

@@ -1,6 +1,7 @@
 import { BaseExecutor } from "./base.js";
 import { PROVIDERS } from "../config/providers.js";
 import { injectReasoningContent } from "../utils/reasoningContentInjector.js";
+import { ANTHROPIC_API_VERSION } from "../providers/shared.js";
 
 // Models that use /zen/go/v1/messages (Anthropic/Claude format + x-api-key auth)
 const CLAUDE_FORMAT_MODELS = new Set(["minimax-m2.5", "minimax-m2.7"]);
@@ -26,7 +27,7 @@ export class OpenCodeGoExecutor extends BaseExecutor {
 
     if (CLAUDE_FORMAT_MODELS.has(this._lastModel)) {
       headers["x-api-key"] = key;
-      headers["anthropic-version"] = "2023-06-01";
+      headers["anthropic-version"] = ANTHROPIC_API_VERSION;
     } else {
       headers["Authorization"] = `Bearer ${key}`;
     }