chore(cli-v2): un-ignore CLI source tree for binary release workflow

The CLI source (242 files, ~14k lines) was gitignored during the
earlier cli→cli-v2 reorg so only the published npm package carried it.
That blocks the GitHub Actions release workflow (release-cli.yml),
which clones the repo fresh on each runner and needs the source to
compile binaries via `bun build --compile`.

Moves the gitignore from root-level to `apps/cli-v2/.gitignore` with
only the usual build artefacts excluded (node_modules, dist, .turbo,
.cache). Source is now in git at apps/cli-v2/src/.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/cli-v2/tests/unit/exit-codes.test.ts

@@ -0,0 +1,13 @@
+import { describe, it, expect } from "vitest";
+import { EXIT } from "~/constants/exit-codes.js";
+
+describe("exit codes", () => {
+  it("SUCCESS is 0", () => { expect(EXIT.SUCCESS).toBe(0); });
+  it("AUTH_FAILED is 2", () => { expect(EXIT.AUTH_FAILED).toBe(2); });
+  it("INVALID_ARGS is 3", () => { expect(EXIT.INVALID_ARGS).toBe(3); });
+  it("INTERNAL_ERROR is 8", () => { expect(EXIT.INTERNAL_ERROR).toBe(8); });
+  it("all codes are unique", () => {
+    const values = Object.values(EXIT);
+    expect(new Set(values).size).toBe(values.length);
+  });
+});