fix(github): add targetFormat to GPT-5.6 Sol/Terra/Luna models (#8951)

Closes #8951
Refs: base-red #9737
fix/8951-github-copilot-gpt56-respons

changelog.d/fixes/8951-fix.plan.md

@@ -0,0 +1 @@
+- fix(github): add targetFormat to GPT-5.6 Sol/Terra/Luna models (#8951)

tests/unit/8951-github-gpt56-responses.test.ts

@@ -0,0 +1,19 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+
+import { GithubExecutor } from "../../open-sse/executors/github.ts";
+
+test("#8951 GitHub GPT-5.6 models must use the Responses endpoint", () => {
+  const executor = new GithubExecutor();
+  const urls = Object.fromEntries(
+    ["gpt-5.6-sol", "gpt-5.6-terra", "gpt-5.6-luna"].map((model) => [
+      model,
+      executor.buildUrl(model, false),
+    ])
+  );
+  assert.deepEqual(urls, {
+    "gpt-5.6-sol": "https://api.githubcopilot.com/responses",
+    "gpt-5.6-terra": "https://api.githubcopilot.com/responses",
+    "gpt-5.6-luna": "https://api.githubcopilot.com/responses",
+  });
+});

tests/unit/provider-registry-github-copilot-targetformat.test.ts

@@ -67,6 +67,9 @@ for (const id of [
   "gpt-5.4-mini",
   "gpt-5.4",
   "gpt-5.5",
+  "gpt-5.6-sol",
+  "gpt-5.6-terra",
+  "gpt-5.6-luna",
   "mai-code-1-flash",
   "gpt-5-mini",
   "oswe-vscode-prime",