fix(github): Enterprise Server pull request URLs can be pasted to check out (#29892)

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

Author: saphid

packages/client-runtime/src/pullRequestLinkInput.test.ts

@@ -173,6 +173,14 @@ describe("parsePullRequestReference", () => {
     expect(parsePullRequestReference(url)).toBe(url);
   });
 
+  it.each([
+    "https://github.acme.test/acme/web/pull/42",
+    "https://git.corp.example/acme/web/pull/42/files?diff=split",
+  ])("accepts GitHub Enterprise Server pull request URL %s", (url) => {
+    expect(parsePullRequestReference(url)).toBe(url);
+    expect(parsePullRequestReference(`gh pr checkout ${url}`)).toBe(url);
+  });
+
   it("accepts gh pr checkout commands with raw numbers", () => {
     expect(parsePullRequestReference("gh pr checkout 42")).toBe("42");
   });

packages/source-control-github/src/shared/definition.ts

@@ -19,7 +19,7 @@ import { gitHubReferenceAutolinks } from "./referenceAutolinks.ts";
 
 const CHECKOUT_COMMAND = /^gh\s+pr\s+checkout\s+(.+)$/i;
 const CHANGE_REQUEST_REFERENCE =
-  /^https:\/\/github\.com\/[^/\s]+\/[^/\s]+\/pull\/(\d+)(?:[/?#].*)?$/i;
+  /^https?:\/\/[^/?#\s]+\/[^/\s]+\/[^/\s]+\/pull\/(\d+)(?:[/?#].*)?$/i;
 
 // GitHub Enterprise Server runs on any hostname, so the `<owner>/<repo>/pull/<n>` route alone
 // identifies a GitHub pull request.