fix: preserve classic openspec version passthrough - #300

Please address the comments from this code review:

## Overall Comments
- In `runCli`, the direct `process.argv[2] === 'classic'` check is a bit brittle; consider using a more explicit argument parsing or Commander hook so subcommand routing stays consistent if the CLI invocation pattern changes (e.g., prefixed global flags).
- The new test spies on `process.stdout.write` but never restores the spy; adding explicit restoration (e.g., via `stdout.mockRestore()` or `vi.restoreAllMocks()` in an `afterEach`) would reduce potential side effects across tests.

## Individual Comments

### Comment 1
<location path="test/app/classic-command.test.ts" line_range="107-127" />
<code_context>
     }
   });
+
+  it('routes Classic group argv before global version parsing', async () => {
+    const stdout = vi.spyOn(process.stdout, 'write').mockImplementation(() => true);
+    runClassicCli.mockResolvedValue({ exitCode: 0, stdout: 'openspec version\n' });
+    const originalArgv = process.argv;
+    const originalExitCode = process.exitCode;
+    process.argv = [process.execPath, 'comet', 'classic', 'openspec', '--', '--version'];
+    process.exitCode = undefined;
+    vi.resetModules();
+
+    try {
+      await import('../../app/cli/index.js');
+      await vi.waitFor(() => {
+        expect(runClassicCli).toHaveBeenCalledWith(['openspec', '--', '--version']);
+        expect(stdout).toHaveBeenCalledWith('openspec version\n');
+        expect(process.exitCode).toBe(0);
+      });
+    } finally {
+      process.argv = originalArgv;
+      process.exitCode = originalExitCode;
+    }
+  });
 });
</code_context>
<issue_to_address>
**suggestion (testing):** Restore the stdout spy after the test to avoid side effects on subsequent tests

This test mocks `process.stdout.write` but never restores it. Even if Vitest resets mocks between tests, we should explicitly restore `stdout` in the `finally` block alongside `process.argv` and `process.exitCode` to avoid unintended interactions with other tests that depend on the original `stdout.write` behavior.

```suggestion
  it('routes Classic group argv before global version parsing', async () => {
    const stdout = vi.spyOn(process.stdout, 'write').mockImplementation(() => true);
    runClassicCli.mockResolvedValue({ exitCode: 0, stdout: 'openspec version\n' });
    const originalArgv = process.argv;
    const originalExitCode = process.exitCode;
    process.argv = [process.execPath, 'comet', 'classic', 'openspec', '--', '--version'];
    process.exitCode = undefined;
    vi.resetModules();

    try {
      await import('../../app/cli/index.js');
      await vi.waitFor(() => {
        expect(runClassicCli).toHaveBeenCalledWith(['openspec', '--', '--version']);
        expect(stdout).toHaveBeenCalledWith('openspec version\n');
        expect(process.exitCode).toBe(0);
      });
    } finally {
      stdout.mockRestore();
      process.argv = originalArgv;
      process.exitCode = originalExitCode;
    }
  });
```
</issue_to_address>