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/unit/translator-helpers-edge.test.js

@@ -0,0 +1,47 @@
+// Locks edge cases flagged in docs 11 §1/§4 that were only covered indirectly.
+import { describe, it, expect } from "vitest";
+import { normalizeClaudePassthrough } from "../../open-sse/translator/helpers/claudeHelper.js";
+import { parseDataUri, encodeDataUri } from "../../open-sse/translator/helpers/imageHelper.js";
+
+describe("normalizeClaudePassthrough — haiku adaptive thinking (docs 11 §1)", () => {
+  it("downgrades adaptive thinking to enabled+budget for haiku models", () => {
+    const out = normalizeClaudePassthrough({ thinking: { type: "adaptive" } }, "claude-haiku-4-5");
+    expect(out.thinking).toEqual({ type: "enabled", budget_tokens: 10000 });
+  });
+
+  it("keeps adaptive thinking for sonnet/opus", () => {
+    const out = normalizeClaudePassthrough({ thinking: { type: "adaptive" } }, "claude-sonnet-4-6");
+    expect(out.thinking).toEqual({ type: "adaptive" });
+  });
+
+  it("hoists mid-conversation system messages into top-level system", () => {
+    const out = normalizeClaudePassthrough({
+      messages: [
+        { role: "user", content: "hi" },
+        { role: "system", content: "be brief" },
+      ],
+    });
+    expect(out.system).toEqual([{ type: "text", text: "be brief" }]);
+    expect(out.messages.every((m) => m.role !== "system")).toBe(true);
+  });
+});
+
+describe("parseDataUri / encodeDataUri (docs 11 §4)", () => {
+  it("parses a base64 data uri", () => {
+    expect(parseDataUri("data:image/png;base64,AAAB")).toEqual({ mimeType: "image/png", base64: "AAAB" });
+  });
+
+  it("tolerates newlines inside base64 payload", () => {
+    expect(parseDataUri("data:image/jpeg;base64,AA\nBB")?.base64).toBe("AA\nBB");
+  });
+
+  it("returns null for http urls and non-strings", () => {
+    expect(parseDataUri("https://x/y.png")).toBeNull();
+    expect(parseDataUri(null)).toBeNull();
+  });
+
+  it("encode/parse roundtrip", () => {
+    const uri = encodeDataUri("image/webp", "ZZZ");
+    expect(parseDataUri(uri)).toEqual({ mimeType: "image/webp", base64: "ZZZ" });
+  });
+});