feat(codex): support GPT-5.6 Max and Ultra overrides

Add "ultra" reasoning level for Codex GPT-5.6 Sol and Terra, and expose
Max for Luna (Luna falls back Ultra to Max since it is not supported
upstream). Scoped to cx/ routes only; Kiro and generic OpenAI routing
unchanged.

tests/unit/codex-fast-capacity.test.js

@@ -69,3 +69,33 @@ describe("Codex fast tier and capacity handling", () => {
     await expect(new Response(peek.replacementBody).text()).resolves.toBe(text);
   });
 });
+
+describe("Codex reasoning normalization", () => {
+  it.each([
+    ["gpt-5.6-sol", "max", "max"],
+    ["gpt-5.6-sol", "ultra", "ultra"],
+    ["gpt-5.6-terra", "max", "max"],
+    ["gpt-5.6-terra", "ultra", "ultra"],
+    ["gpt-5.6-luna", "max", "max"],
+    ["gpt-5.6-luna", "ultra", "max"],
+  ])("normalizes %s effort %s to %s", (model, effort, expected) => {
+    const body = new CodexExecutor().transformRequest(model, {
+      model,
+      input: "hi",
+      reasoning: { effort },
+    }, true, {});
+
+    expect(body.reasoning.effort).toBe(expected);
+  });
+
+  it("resolves review models before applying the reasoning matrix", () => {
+    const body = new CodexExecutor().transformRequest("gpt-5.6-terra-review", {
+      model: "gpt-5.6-terra-review",
+      input: "hi",
+      reasoning_effort: "ultra",
+    }, true, {});
+
+    expect(body.model).toBe("gpt-5.6-terra");
+    expect(body.reasoning.effort).toBe("ultra");
+  });
+});