feat: currentAuthor() carries git user.email — fail-open identity (F5 SLICE-2, #14)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

test/identity.test.ts

@@ -0,0 +1,25 @@
+import { describe, it, expect, beforeAll, afterAll } from "vitest";
+import * as fs from "node:fs";
+import * as os from "node:os";
+import * as path from "node:path";
+import { execFileSync } from "node:child_process";
+import { gitUserEmail } from "../src/identity";
+
+let repo: string;
+
+beforeAll(() => {
+  repo = fs.mkdtempSync(path.join(os.tmpdir(), "cowriting-identity-"));
+  execFileSync("git", ["init"], { cwd: repo, stdio: "ignore" });
+  execFileSync("git", ["config", "user.email", "rung@example.org"], { cwd: repo });
+});
+afterAll(() => fs.rmSync(repo, { recursive: true, force: true }));
+
+describe("gitUserEmail (F5 SLICE-2)", () => {
+  it("reads the workspace git config user.email", () => {
+    expect(gitUserEmail(repo)).toBe("rung@example.org");
+  });
+
+  it("fails open (undefined) when git cannot run there", () => {
+    expect(gitUserEmail("/nonexistent-dir-xyz")).toBeUndefined();
+  });
+});